don't care about pypy results in travis build

.travis.yml

@@ -10,6 +10,14 @@ python:
   - 3.3
   - pypy
 
+branches:
+  only:
+    - master
+
 install: pip install .
 
 script: CFLAGS=-O0 python runtests.py -vv
+
+matrix:
+  allow_failures:
+    - python: pypy