Stubbed PriorityQueue classes and tests.
Implemented JavaPriorityQueue.
Implemented non-blocking MutexPriorityQueue.
Updated YARD docs for PriorityQueue.
Moved OptionsParser to its own file to prevent recursive require statements.
Concurrent::timer and global timer pool now use TimerSet.
Complete specs and YARD doc for TimerSet and Concurrent::timer
Merge pull request #52 from jdantonio/refactor/with-ste

Implemented TimerSet executor and updated Concurrent::timer