Travis: run tests on pypy; install regex for CPython.

Author: rczajka

.travis.yml

@@ -5,9 +5,11 @@ python:
   - "3.2"
   - "3.3"
   - "3.4"
+  - "pypy"
 # command to install dependencies
 install:
   - pip install -r requirements.txt
   - python setup.py -q install
+  - if [[ ! $TRAVIS_PYTHON_VERSION == pypy ]] ; then pip install regex; fi
 # command to run tests
-script: nosetests
+script: nosetests