Merge branch 'dev' of https://github.com/GoodBoyDigital/pixi.js into dev

Reset Alpha for CanvasRenderer

Merge pull request #531 from alvinsight/dev ...

Dived into WebGLRenderer, fixes and docs

A nice getter/setter for our lovely users

Dived into WebGLRenderer, fixes and docs

return empty rect if container has no visible children

Allow texture to not be flipped

jslinted code

Docs updated ...

Fixed issue where alpha not being set correctly in canvas spriteBatch
Fixed issue where previous stage events did not get removed correctly

Merge pull request #529 from alvinsight/dev ...

Finally, a bit of refactoring, but obviously, docs :)

Typos and Started tackling the WebGL, and tests

Docs :)

Fixed, finally adapted to the dev branch

Manually merge #522 from @qzix13

Added auto prevent default variable to pixi constants

Mad cross origin on by default to fix ie11 issue and make life generally easier

Added constant for interaction frequency

Fixed premultiplied alpha - for webGL transparent canvas

Added clear rect to transparent canvas renderer

Jshinted code

Finished first pass of webGL destroy functions

Fixed render texture issue where textures not getting uploaded to GPU before render

Jshinted code ...

also tweaked BaseTexture.fromCanvas function

Added fromCanvas to base texture ...

added destroy function to webGLRenderer (WIP)

Implemented texture caching for fromCanvas method

update scale modes constants

Forgot to update that one!

Fix texture scaling in canvas renderer

Tweaked mouse up interaction to work inline with expectations ...

commented out unused {}

Fixed hoever interaciton inconsistency ...

Also changed canvas renderer to use fillRect instead of clearRect as
its faster and works with the new alpha property that canvas has