Merge pull request #78 from methane/travis-pip-cache

Enable travis caching for pip cache
diff --git a/.travis.yml b/.travis.yml
index 29ffae4..446dc6f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,7 @@
 language: python
 python: 2.7
 sudo: false
+cache: pip
 env:
   matrix:
   - TOX_ENV=py26