Change target compatibility from 1.5 to 1.6

https://github.com/Netflix/RxJava/issues/153
Merge pull request #155 from benjchristensen/issue-153

Change target compatibility from 1.5 to 1.6
Implemented toIterable method
Static method plus javadoc
Merge pull request #156 from mairbek/toIterable

Implemented ToIterable Operation
Configuring travis ci