Amend .travis.yml file to do doc building and publishing.
Amend .travis.yml file to do doc building and publishing.

Add after-success chunk to take care of doxygen documentation building and publishing into the gh-pages branch of the repo. Currently uses explicit calls to doxygen -- next step to integrate doc building as a cmake target. Currently uses encrypted version of Yifei"s github credentials for purposes of committing and pushing changes.

dnanexus-rnd/GLnexus,dnanexus-rnd/GLnexus,dnanexus-rnd/GLnexus