Dependency update: RxJava 1.1.3.

Notable changes:

• fixed first not unsubscribing the Iterable sequence
• fixed last calling hasNext one extra time
• added firstOrDefault operator
• added lastOrDefault operator
• updated dependency on RxJava to version 1.1.2

Notable changes:

• Added missing skip operator
• Bumped RxJava dependency to 1.1.0

Refactored the ixjava-experiment into a full and proper ixjava project.