Reduce some logic redundancy in clearRect/fillRect code for Canvas...?

Topic.
Update CanvasRenderer.js
Update CanvasRenderer.js
Fixed Strip Alpha bug
Fixed render texture bug
added custom shader
Merge pull request #996 from agamemnus/patch-5

Reduce some logic redundancy in clearRect/fillRect code for Canvas...?
tempCommmit
put batch shader back to normal
object direct comparison for textures
removed emptyTexture object
Added docs to shader property
Merge branch 'dev-customshader' into dev

Conflicts:
	bin/pixi.dev.js
	bin/pixi.dev.js.map
	src/pixi/textures/RenderTexture.js
Fixed webGL tiling sprite bug
fixed blendmode mapping in canvas bug
fixed non po2 tiling texture bug
Linted code
republished files
tweaked so that filter offset gets set
Merge branch 'dev' of https://github.com/GoodBoyDigital/pixi.js into dev