BLD: Add sphinx build to .travis.yml
BLD: Add sphinx build to .travis.yml

Fixes #179

josenavas/QiiTa,adamrp/qiita,ElDeveloper/qiita,antgonza/qiita,antgonza/qiita,adamrp/qiita,ElDeveloper/qiita,biocore/qiita,squirrelo/qiita,squirrelo/qiita,antgonza/qiita,josenavas/QiiTa,squirrelo/qiita,adamrp/qiita,antgonza/qiita,adamrp/qiita,josenavas/QiiTa,biocore/qiita,ElDeveloper/qiita,biocore/qiita,josenavas/QiiTa,ElDeveloper/qiita,biocore/qiita,squirrelo/qiita