travis: Build against pypy3

See http://docs.travis-ci.com/user/languages/python/#PyPy-Support

Author: sils

.travis.yml

@@ -2,6 +2,7 @@ language: python
 
 python:
     - "2.7"
+    - "pypy3"
     - "3.2"
     - "3.3"
     - "3.4"