Merge branch 'origin/develop'

Release v0.8
Only run the tests
Move test_args to tox.ini
Fix doc-strings and github3.login
Add a documented example
Comment the example code

A bit of clarification
Fix tests
Allow for higher versions of pytest
Add example to index

[ci skip]
Bump the copyright year
Update CONTRIBUTING.rst

Add not about how to use the issue tracker
Expose the stargazers count for repositories

I'm now using repo._json_data['stargazers_count'], which is a hack.
Making it part of the proper API.
Bump version and update history for 0.8.1