Created start map infrastructure
Also converted dependency-installer into a ruby script
Initial push towards a system-centric architecture
- Main code is all in the Game class now
- Game class has systems
- Systems use wrappers (eg. Display class)
More work towards entities (#3, #5)
- Game file defines a set of components
- Display system draws display components
- Display system can fill the screen on request
- Game.create_entities_for creates walls
- Display has a width/height
Resolve #8: Colour Strategy

- Colour is all RGB (added `Colour` class)
- Colour strategy is approximate (Windows) or use up to 255 (Linux)
- Terminal quits if screen is too small
- Quit by pressing escape