RenderTexture update

RenderTexture added (webGL and Canvas)
WebGL Render rearchitected - a little faster :)
Pivot added to DisplayObject
docs updated
grunt file updated
text update
Merge branch 'master' of https://github.com/GoodBoyDigital/pixi.js

Conflicts:
	src/pixi/text/Text.js
Merge branch 'Dev'

Conflicts:
	src/pixi/text/Text.js
Render Texture added

Render texture finished
custom render item added
pivot added to display object

grunt file updated
docs updated
Text update
Render Texture bug fix

Fixed bug with rendering single sprite
Example updated