extended httpImagePath to be compatible with downsampling if it ends with a /
removed install scripts antipattern (see man npm-scripts)
zero values should not have units
switch to graceful-fs to handle large number of images

Conflicts:
	package.json
	src/builder.coffee
Change: Ignore specific warnings when ImageMagick convert and composite.
switch from composite to convert(-composite) to create the final sprite in bulks

Conflicts:
	src/imagemagick.coffee