Fix destroy method of WebGLRenderer.js
this.view doesn't have off method.
Fix destroy method test of WebGLRenderer
If we cannot create WebGLRenderer, we cannot test destroy method
Fixed destroy method test of WebGLRenderer
Merge pull request #1110 from jonime/dev

Fix destroy method of WebGLRenderer.js
Updates

ensured all float32arrays use PIXI.Float32Array
fixed missing prototype on unloadFromGPU
fixed Graphics cacheAsBitmap alpha issue
fixed strip alpha issue
Merge branch 'dev' of https://github.com/GoodBoyDigital/pixi.js into dev