add Map explored_tiles and Tile inView properties
update renderAll() to look at explored Tiles and those inView
new inView property for Actors
distance between two points utility
update field of view for a map
update Map field of view on player move, only draw visible Actors
refresh the fov on level warps
use the TORCH_RADIUS constant for view range
add helpers to get line segments, and check for line of sight
perform line of sight test in updateFieldOfView()
Merge branch 'master' into fov

Conflicts:
	Game.py
Merge branch 'master' of github.com:DebianJoe/advanced

Conflicts:
	ApplicationLibtcod.py
	Game.py