Fix minor typo in MultiplexAsyncProcessor docs and update license
Fix minor typo in MultiplexAsyncProcessor docs and update license

Summary: Oops.

Differential Revision: D33639019

fbshipit-source-id: 133b6ee8eb758daa50532be6b56af862cc1e2d20

facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift,facebook/fbthrift