bug with requestAnimationFrame
small code for direct link to a level
add 'ceiling' to levels
create management of png and jpg textures (more compatible levels) and better management of limits
conditional display of level limits (borders) => no display when not on the border of a level
improvement of sprite animations and management of changing theme
kill moto on wrecker contact
sprites: default size and position when no size and positions into theme or lvl
remove debug
improve collision box of moto (no more stable wheeling)
better Constants.coffee with activation or desactivation of collisions
correct scroll direction in firefox
debug lowercase on production
Replaying : pause the game at the beginning

Signed-off-by: Nicolas Adenis-Lamarre <nicolas.adenis.lamarre@gmail.com>
Merge branch 'master' into replays

Signed-off-by: Nicolas Adenis-Lamarre <nicolas.adenis.lamarre@gmail.com>

Conflicts:
	bin/xmoto.js
	index.html
	src/constants.coffee
	src/main.coffee