Updated pytz to 2014.7. Fixed Travis CI, #298

Updated pytz to 2014.7

Note that I wasn't sure how to update the README.md to reflect this change, since the original gaepytz library on code.google.com is pretty old. What I have done is forked gae-pytz on github, added this update, and sent a pull request there. My fork is at https://github.com/movero/gae-pytz (which includes this update), and the original repo is at https://github.com/potatolondon/gae-pytz (where I just submitted the pull request).