Decoupled canvas client dimensions from drawing buffer dimensions.
addressing minor issues with pull request
Fix #1160, and clear the canvas correctly.

The canvas used to be cleared by "resize" which would write
to the size even if it was unchanged.  Now that this is no
longer the case, it must be cleared manually.
Fixing issue where pick rays were miscomputed when the browser was zoomed
Fix issue #1166.
adding support for window.devicePixelRatio

Firefox 23 updates window.devicePixelRatio when zooming; Chrome 29 does
not. Chrome 31 does, but that's not stable yet.
Fix GeometryInstanceAttribute memory pressure

Make `Color.toBytes`, `ColorGeometryInstanceAttribute.toValue`, and `ShowGeometryInstanceAttribute.toValue` take an optional result parameter.  This avoids very costly TypedArray allocations each frame.
Merge remote-tracking branch 'agi/master' into browser_zoom_fix

Conflicts:
	CHANGES.md
	Source/Scene/Camera.js
	Specs/Scene/CameraControllerSpec.js
Merge pull request #1176 from AnalyticalGraphicsInc/geometry-memory-pressure

Fix GeometryInstanceAttribute memory pressure
billboard sizing fix
Merge pull request #1172 from AnalyticalGraphicsInc/issue1160

Fix #1160, and clear the canvas correctly.
Merge pull request #1162 from balefrost/browser_zoom_fix

Decoupled canvas client dimensions from drawing buffer dimensions.
Added Dan Yankowsky to CONTRIBUTORS.md
Tweak CHANGES.md
Fix CZML object deletion
Remove unused variable.
Merge pull request #1179 from AnalyticalGraphicsInc/unused-var

Remove unused variable.
Merge pull request #1178 from evax/fixCzmlDelete

Fix CZML object deletion
Put back unit test for CZML `delete` packet.
Merge pull request #1174 from AnalyticalGraphicsInc/issue1166

Fix issue #1166.