made the temp wrapper class final
Added documentation
added asserts for repeatedly completing a future

Do we need exceptions?
simplified the implementation of zip, leveraging the power of (flat)map
added fold to FutureUtils, including tests
added execution context to fold, more tests
improved the traverse implementation, now powered by fold
added Future.completeAfter
added FutureUtils.firstCompletedOf
added FutureUtils.sequence, sequence param to Array because of compiler issues