making installation instructions more newbie friendly

[alecristia]

Is your feature request related to a problem? Please describe.

Two similar & related problems:

• If one directly clicks on eg macos installation, one skips the important Note about conda installation
• Neither the note nor the macos installation instructions holds one hand to understand that output like the following means conda isn't installed:

conda env create -f env.yml

Traceback (most recent call last):
File "/Users/acristia/opt/miniconda2/bin/conda", line 13, in
sys.exit(main())
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/cli/main.py", line 149, in main
from ..exceptions import conda_exception_handler
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/exceptions.py", line 19, in
from ._vendor.auxlib.entity import EntityEncoder
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/_vendor/auxlib/entity.py", line 253, in
from .collection import AttrDict, frozendict, make_immutable
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/_vendor/auxlib/collection.py", line 10, in
from .compat import isiterable, iteritems, odict, text_type
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/_vendor/auxlib/compat.py", line 10, in
from ._vendor.five import WhateverIO as StringIO, with_metaclass
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/_vendor/auxlib/_vendor/five.py", line 80, in
absolute_to_nanoseconds = CoreServices.AbsoluteToNanoseconds
File "/Users/acristia/opt/miniconda2/lib/python2.7/ctypes/init.py", line 379, in getattr
func = self.getitem(name)
File "/Users/acristia/opt/miniconda2/lib/python2.7/ctypes/init.py", line 384, in getitem
func = self._FuncPtr((name_or_ordinal, self))
AttributeError: dlsym(RTLD_DEFAULT, AbsoluteToNanoseconds): symbol not found

conda --version

Traceback (most recent call last):
File "/Users/acristia/opt/miniconda2/bin/conda", line 13, in
sys.exit(main())
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/cli/main.py", line 149, in main
from ..exceptions import conda_exception_handler
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/exceptions.py", line 19, in
from ._vendor.auxlib.entity import EntityEncoder
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/_vendor/auxlib/entity.py", line 253, in
from .collection import AttrDict, frozendict, make_immutable
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/_vendor/auxlib/collection.py", line 10, in
from .compat import isiterable, iteritems, odict, text_type
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/_vendor/auxlib/compat.py", line 10, in
from ._vendor.five import WhateverIO as StringIO, with_metaclass
File "/Users/acristia/opt/miniconda2/lib/python2.7/site-packages/conda/_vendor/auxlib/_vendor/five.py", line 80, in
absolute_to_nanoseconds = CoreServices.AbsoluteToNanoseconds
File "/Users/acristia/opt/miniconda2/lib/python2.7/ctypes/init.py", line 379, in getattr
func = self.getitem(name)
File "/Users/acristia/opt/miniconda2/lib/python2.7/ctypes/init.py", line 384, in getitem
func = self._FuncPtr((name_or_ordinal, self))
AttributeError: dlsym(RTLD_DEFAULT, AbsoluteToNanoseconds): symbol not found

Describe the solution you'd like
Perhaps just adding something like the following "if you get any error, it probably means conda isn't installed" with a link to the conda install instructions