Add build_doc.sh script to .travis.yml

I still need to add the encrypted token so that it actually works
Add encrypted token for Travis
build_doc.sh will be one level up
Debugging
Hopefully fix build_doc calling in .travis.yml
Print a message in build_doc in a pull request
Rename build_doc.sh to update-gh-pages.sh
Merge pull request #22 from asmeurer/travis-build-docs

Add build_doc.sh script to .travis.yml
Checkout origin/gh-pages
Checkout origin_token/gh-pages
Run update-gh-pages in the script section, not after_success

It will still only run if the previous commands pass, but this way, if it
fails, the build will fail.
Add some debugging to update-gh-pages
Fix typo
Try printing the ls output
More debug output in update-gh-pages
More debugging
Factor out common components in update-gh-pages
cd to the right directory
We don't need to specify Python in .travis.yml, since we use Miniconda

Hopefully this doesn't break it.
Debugging