Initial implementation and wiring of the buffer operators.
Restored static imports in Observable.
Added static create methods to BufferOpenings and BufferClosings.
Added license header to OperationBuffer.
Changed default scheduler used in buffer operation and removed printStackTrace call
Added JavaDoc and moved public helper classes of OperationBuffer class to rx.util package.
Improved buffer operation test cases with checks for empty buffers.
Merged master into buffer-operation branch
Merge pull request #281 from michaeldejong/operation-buffer

Operation: buffer