todo: elaborate and organize these notes

Building allegro 4 in Linux (and probably most UNIX-like systems):
- need dependencies like libx11-dev, build-essential (You can follow
  the failure notes of the cmake process to see what you need.)

- After make install, you have to do:
	sudo ldconfig
  so that the shared allegro library can be found by allegro-based
  programs, which in this case is the nvaderz game.
