Add missing pip commands.

Travis docs say this isn't necessary, fails without https://docs.travis-ci.com/user/languages/python#pip

.travis.yml

@@ -7,6 +7,8 @@ before_install:
   - "/sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -ac -screen 0 1280x1024x16"
 
 install:
+  - pip install .
+  - pip install -r requirements.txt
   - pip install coverage
 
 script: