experiment with recent rtd theme

.travis.yml

@@ -5,7 +5,7 @@ python:
 
 install: 
   - pip install --user sphinx # sphinx_rtd_theme
-  - python -m pip install https://github.com/rtfd/sphinx_rtd_theme/archive/master.zip -U
+  - sudo python -m pip install https://github.com/rtfd/sphinx_rtd_theme/archive/master.zip -U
 
 script: bash ./build_and_deploy.sh