Add a test of chaining generators using successive yield*s.
Add a test of chaining generators using successive yield*s.

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