Minor WebGL tweaks.
First stab at WebGL render to texture.

Not bad so far, though it's rendering upside down for some reason.
First pass at WebGLTexture.readPixels/writePixels.

Not yet working properly.
WebGL read/writePixels fixes.
Fix for upside down render to texture.
Oops, go back to private, you.
The viewport needs to be updated when setting up the framebuffer.
Implement WebGLGraphics.translate/scale/rotate.
Added Mask blend mode
Changed HtmlExternal to bind functions to the container

This is more consistent with the way it works for Flash, and
also allows works when using multiple Flambe instances.
flambe.embed can take a callback that is fired when embedding is complete
Initially add canvas with no width/height

This is because some browsers (e.g. chrome) give a default width/height
that can cause it to become larger than its parent, breaking stage size
detection.
Fix some issues when using with haxe 3 rc
Initial changes to support a shared context in flash mode
Don't alter the stage when using a shared context
Initial changes to support a shared context in HTML mode

At the moment the shared flag has no effect, but a context can be passed in.
Fix initialising a Flash stage when no context is given
Added a method to Texture to get the bounds of an area matching a color

Behaves similarly to BitmapData#getColorBoundsRect
(http://help.adobe.com/en_US/as2/reference/flashlite/WS5F7E996C-A0F6-4d89-BC17-69622D209F21.html).
Catch some unhandled errors

- Trying to read pixels from a texture larger than the stage throws an
  exception in constrained mode.  Width/height are now clipped to stage
  width/height when reading pixels (the alternative would be to render
  each area separately and aggregate the pixel data, but this would
  probably not be performant).

- With multiple flambe instances on a page, an exception is thrown when
  trying to generate multiple AudioContexts.
Add swc target