Minor readme cleanup
Minor readme cleanup

Summary: Minor cleanup such as adding missing punctuation to the Thrift README on GitHub.

Reviewed By: yfeldblum

Differential Revision: D13330189

fbshipit-source-id: 481cee09bdb29e5558881d3131921b458df33b75

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