Integration tests

[rexim]

I think we can implement them:

• just start the game with pacmacs-start;
• replay some test case with pacmacs-left/right/up/down;
• quit the game with pacmacs-quit;
• assert the game state.

The only problems are

• Image displaying on CI (we can probably mock that)
• Timing of the actions

[rexim]

Regarding displaying images on CI, travis supports xvfb on their machines: https://docs.travis-ci.com/user/gui-and-headless-browsers/

It only remains to use emacs builds that support GUI, 'cause the builds from EVM are the console only ones.