Implement XmlOverlaySpec.
Add comments to XmlOverlaySpecRenderer.
Changed IllegalArgumentException to ParsingException
Merge branch 'refs/heads/xmloverlayspec'

Conflicts:
	Hipsterrific/src/com/hipsterrific/FaceDetector/MoustacheOverlaySpec.java
	Hipsterrific/src/com/hipsterrific/app/DisplayImageActivity.java