TravisCI integration

[Seanny123]

First draft of attempting to integrate to TravisCI.

Todo:

• [ ] Fix failing tests
• [ ] Reduce code duplications by importing most of test_examples.py from nengo

[Seanny123]

@jgosmann I messed up rebasing again, but aside from that, I'm a bit confused about how to resolve the remaining pylint errors. Would you mind taking a look?

[jgosmann]

Well those should be solved by pretty much what it is recommending:

1. Add the r prefix to the (doc) strings it is complaining about in nengo_extras.learning_rules.
2. Remove the unused import of StringIO in nengo_extras.utils.

[Seanny123]

Well those should be solved by pretty much what it is recommending

I literally have no idea why I was confused last night.

[tbekolay]

This was superseded by the now merged #68.