Contribution guidelines

Running tests

Use tox:

pip install tox
tox

Checkout the master branch.
Pull the latest changes from origin.
Make sure check-manifest is happy.
Increment the version number.
Set the correct title for the release in HISTORY.rst.
Update the AUTHORS.rst file with new contributors:
```
lancet contributors AUTHORS.rst
```
Commit everything and make sure the working tree is clean.
Push everything to github and make sure the tests pass on Travis:
```
git push origin master
```
Build and upload the release:
```
python setup.py publish
```
Tag the release:
```
lancet tagver
```
Push everything to github:
```
git push --tags origin master
```
Add the title for the next release to HISTORY.rst