Unit tests

[FiniteReality]

Unit tests are needed to ensure the code I'm writing actually works. This involves adding some stuff to the CMakeLists to allow building of unit tests.

• [x] Add unit test support to CMakeLists
• [x] Use Travis CI to build disccord
• [x] Use Travis CI to run tests
• [x] Write preliminary unit tests

[unleashy]

I like Catch, what do you think?

[FiniteReality]

At this point the basic framework for unit testing has been written, so what we need now is complete unit tests for things which aren't currently tested or are not tested fully.