BLD: Update travis matrix.

Author: Scott Sanderson

.travis.yml

@@ -1,12 +1,14 @@
 language: python
 sudo: false
 python:
+  - "2.7"
   - "3.4"
   - "3.5"
 
 before_script:
   - pip install tox
 
 script:
+  - if [[ $TRAVIS_PYTHON_VERSION = '2.7' ]]; then tox -e py27; fi
   - if [[ $TRAVIS_PYTHON_VERSION = '3.4' ]]; then tox -e py34; fi
   - if [[ $TRAVIS_PYTHON_VERSION = '3.5' ]]; then tox -e py35; fi