Fix repo references in the README

Author: Jay Zeschin

README.md

@@ -13,8 +13,8 @@ To use this buildpack, you should prepare .buildpacks file that contains this bu
     ...
 
     $ cat .buildpacks
-    https://github.com/shunjikonishi/heroku-buildpack-ffmpeg
-    https://github.com/heroku/heroku-buildpack-play
+    https://github.com/jayzes/heroku-buildpack-ffmpeg
+    https://github.com/heroku/heroku-buildpack-ruby
 
     $ heroku create --buildpack https://github.com/ddollar/heroku-buildpack-multi