Allow running tests via "rake test"
Keep raw config json data internal
Keep application running until window is closed by the user
Give our window a nice title!
Add beginnings of input mapping subsystem

Inputs are handled in a key -> event -> callback chain. Code creates a
new Input object, maps events, and will have key -> event mapping be
taken care of by configuration files.
Make sure code is built before running full test suite
Convert tests to use testify library

Gives me the "assert" syntax that's so much easier to read than if
statements and error messages. Also has much nicer error and failure
output messages.
Add top-level tasks for the rest of the entries
Ensure multiple keys can point to the same event
Build and use internal list of key constants

I don't want glfw to be spread everywhere through out the code, so
setting up a list of constants, mapped to glfw values, that should be
used instead.
Switch default rake task to "test"

This is the default I've used for a long time, so makes sense work this
way and explicitly say "run" when I want to run the application.