[ASDisplayNode convertRect:fromNode:] hotfix

`_calculateTransformFromReferenceToTarget()` was being called incorrectly! :+1:
Add ASDisplayNode.cornerRadius
Merge pull request #103 from aleclarson/facebook

Add ASDisplayNode.cornerRadius
Merge pull request #102 from aleclarson/patch-1

[ASDisplayNode convertRect:fromNode:] patch
ASMultiplexImageNode.

Initial open-source release of ASMultiplexImageNode.  Documentation and
example code forthcoming.
Disable Travis iOS 7 builds.