Merge pull request #162 from cclauss/patch-6

Updated pypy to 2.3.1 and added pypy3

Readme.md

@@ -46,6 +46,7 @@ Runtime options include:
 
 - python-2.7.8
 - python-3.4.1
-- pypy-1.9 (experimental)
+- pypy-2.3.1 (unsupported, experimental)
+- pypy3-2.3.1 (unsupported, experimental)
 
 Other [unsupported runtimes](https://github.com/heroku/heroku-buildpack-python/tree/master/builds/runtimes) are available as well.