diff --git a/README.md b/README.md
index 89e4c91..e0d76e8 100644
--- a/README.md
+++ b/README.md
@@ -19,18 +19,21 @@ done before officially releasing on PyPI.
 ```python
 import mutations
 
-class EmailToBouncedMessage(mutations.Mutation):
+class UserSignup(mutations.Mutation):
+    """Define the inputs to your mutation here. """
     email = mutations.fields.CharField(required=True)
-    send_welcome_email = mutations.fields.Boolean(required=False, default=False)
+    full_name = mutations.fields.CharField(required=True)
+    send_welcome_email = mutations.fields.Boolean(required=False, default=True)
 
-    def validate_email_object(self):
+    def validate_email_address(self):
         """Custom validation for a field.
 
         If you encounter any validation errors and want to raise, you should
         raise mutation.ValidationError or some sublcass thereof. Otherwise, it
         assumes there were no problems.
 
-        Any function beginning with `validate_` is assumed to be a validator function.
+        Any function beginning with `validate_` is assumed to be a validator
+        function and will be run before the mutation can execute.
         """
         if not self.email.is_valid():
             raise mutations.ValidationError("email_not_valid", "Email is not valid.")
@@ -41,27 +44,26 @@ class EmailToBouncedMessage(mutations.Mutation):
         This method does the heavy lifting. You can call it by calling .run() on
         your mutation class.
         """
-        new_object = "this is the new object"
+        user = User.objects.create(email=self.email, name=self.full_name)
         if self.send_welcome_email:
-            # You can access the inputs here, like this.
             PersonalEmailServer.deliver(recipient = self.email)
 
-        return new_object
+        return user
 ```
 
 ## Calling Commands
 
 ```python
->>> result = EmailToBouncedMessage.run(email=email, send_welcome_email=True)
+>>> result = EmailToBouncedMessage.run(email=email, full_name="Bob Boblob")
 >>> result.success
 True
 >>> result.value
-"this is the new object"
+<User id=...>
 >>> result.errors
 ```
 
 ```python
->>> result = EmailToBouncedMessage.run(email = None)
+>>> result = EmailToBouncedMessage.run(email=None)
 >>> result.success
 False
 >>> result.errors
diff --git a/TODO.md b/TODO.md
new file mode 100644
index 0000000..80ad4dc
--- /dev/null
+++ b/TODO.md
@@ -0,0 +1,31 @@
+# TODO:
+
+List of things we need to do/fix before releasing on PyPI:
+
+### General
+
+- [ ] Make sure you cannot create a field called "inputs"
+- [ ] Make sure it raies if you give it a kwarg it doesn't know about.
+- [ ] Think of a better way to pass exceptions. I don't like passing the
+    `nameduple` in the Exception.
+
+- [ ] Support for Python 2.X.
+- [ ] Update README and provide more useful examples.
+- [ ] Put test requirements into `test-requirements.txt`
+- [ ] Make execute an `@abstractmethod`, so that an error gets raised if
+    you don't define `execute` in your mutation subclass.
+- [ ] Release on pypi.
+- [ ] Support for running commands in an atomic (all or nothing) fashion,
+    perhaps using a contextmanager.
+- [x] Create setup.py file
+- [x] Add `__version__`
+- [x] Test that exceptions can be raised when you `run`.
+
+
+### Testing
+
+- [ ] Make sure default values get overridden if there's a user-provided value.
+- [ ] Make sure command fails if you provide unexpected inputs.
+- [ ] Make sure `Mutation.__getattr__` raises if you ask it for something that does not exist.
+
+
diff --git a/mutations/__init__.py b/mutations/__init__.py
index 3f30c84..d41549c 100644
--- a/mutations/__init__.py
+++ b/mutations/__init__.py
@@ -1,3 +1,3 @@
 from .core import Mutation
 
-__version__ = '0.1.0'
\ No newline at end of file
+__version__ = '0.1.0'
diff --git a/mutations/core.py b/mutations/core.py
index d0d6b0c..86eff1f 100644
--- a/mutations/core.py
+++ b/mutations/core.py
@@ -7,6 +7,7 @@
 
 Result = namedtuple('Result', ['success', 'return_value', 'errors'])
 
+
 class MutationBase(type):
     def __new__(mcs, name, bases, attrs):
         attrs.update({
@@ -30,9 +31,10 @@ def __new__(mcs, name, bases, attrs):
         for v in extra_validator_list:
             validator = attrs.pop(v)
             attrs['extra_validators'][v].extend(wrap(validator))
-            
+
         return super().__new__(mcs, name, bases, attrs)
 
+
 class Mutation(metaclass=MutationBase):
     def __init__(self, name, inputs=None):
         self.name = name
diff --git a/mutations/error.py b/mutations/error.py
index 33cb92a..a696fc8 100644
--- a/mutations/error.py
+++ b/mutations/error.py
@@ -1,5 +1,10 @@
 from collections import UserDict, namedtuple
 
+
+class MutationError(Exception):
+    pass
+
+
 class ErrorDict(UserDict):
     def __init__(self, *args, default_factory=list, **kwargs):
         self.default_factory = default_factory
@@ -11,6 +16,8 @@ def __getitem__(self, k):
         return self.data[k]
 
     def __add__(self, other):
+        if self.default_factory != other.default_factory:
+            raise MutationError("Cannot add two ErrorDicts with different default_factories.")
         context = {}
         context.update(self)
         for key, val in other.items():
@@ -25,12 +32,9 @@ def is_empty(self):
         return not bool(self.data)
 
 
-class MutationError(Exception):
-    pass
-
-
 ErrorBody = namedtuple('ErrorBody', ['err', 'msg'])
 
+
 class ValidationError(MutationError):
     def __init__(self, err=None, msg=None, *args, **kwargs):
         self.err = err
diff --git a/mutations/fields.py b/mutations/fields.py
index 237e358..5b27157 100644
--- a/mutations/fields.py
+++ b/mutations/fields.py
@@ -55,4 +55,4 @@ def __init__(self, instance_of, *args, **kwargs):
 
     @property
     def validators(self):
-        return validators.InstanceValidator(instance_of=self.instance_of)
\ No newline at end of file
+        return validators.InstanceValidator(instance_of=self.instance_of)
diff --git a/mutations/sample.py b/mutations/sample.py
deleted file mode 100644
index 3498f68..0000000
--- a/mutations/sample.py
+++ /dev/null
@@ -1,7 +0,0 @@
-import mutations
-
-
-class SimpleMutation(mutations.Mutation):
-    name = mutations.fields.CharField()
-    email = mutations.fields.CharField()
-    location = mutations.fields.CharField(required=False)
\ No newline at end of file
diff --git a/mutations/util.py b/mutations/util.py
index fd209b9..88adedd 100644
--- a/mutations/util.py
+++ b/mutations/util.py
@@ -1,4 +1,4 @@
 def wrap(item):
     if not isinstance(item, (list, tuple)):
         return [item]
-    return item
\ No newline at end of file
+    return item
diff --git a/mutations/validators.py b/mutations/validators.py
index 09c8818..902929d 100644
--- a/mutations/validators.py
+++ b/mutations/validators.py
@@ -51,4 +51,4 @@ def is_valid(self, *args, **kwargs):
 
 class SavedObjectValidator(ValidatorBase):
     def is_valid(self, obj):
-        return obj.pk is not None and obj.pk != ''
\ No newline at end of file
+        return obj.pk is not None and obj.pk != ''