Python 3 (with tests)

[tysonclugg]

@matclayton

• Drops support for Django 1.7 (not supported, conflicts with jsonfield 2.0).
• Add support Python 3.3, 3.4, 3.5 and 3.6.
• Also adds config for Travis CI.
• Second class support for PyPy (tox tests pass) since Travis CI PyPy install is broken.
• All tests passing. 🙂

Test results from Travis CI at https://travis-ci.org/tysonclugg/django-experiments:

Test results from tox on my machine:

[matclayton]

Thanks not looked at this in depth, more than happy to drop 1.7! We currently use codeship for CI, so I'd like to get it working on there as well. I'll need to take some time and figure it out, but once thats done, I'm happy to merge/ship this out.

[tysonclugg]

I tried to look at your Codeship builds, but they're not public? Travis is free for open source...

[matclayton]

Great point, I have no idea how we didn't spot that! I'll try and open it up.

[tysonclugg]

This PR resolves the following issues:

• Is Python3 supported? #143 Is Python3 supported?
• Hardcoded version of 'mock' and 'django-modeldict-yplan' breaks people's projects #148 Hardcoded version of 'mock' and 'django-modeldict-yplan' breaks people's projects
• Add backwards compatible python3 support #157 Add backwards compatible python3 support