Make bin/regenerator read from STDIN when no file name given.
Make bin/regenerator read from STDIN when no file name given.

Closes #125.

rafaelstz/regenerator,facebook/regenerator,kittens/regenerator,kittens/regenerator,RReverser/js-goto-transpiler,Jericho25/regenerator,Jericho25/regenerator,rafaelstz/regenerator,facebook/regenerator,facebook/regenerator,liviuignat/regenerator,juliocanares/regenerator,liviuignat/regenerator,juliocanares/regenerator,RReverser/js-goto-transpiler,sebmck/regenerator,sebmck/regenerator