Hasn't been run since the travis days.
Now managed through a deploy key rather than an access token to limit scope to
a single repo. Private key is stored in qTox/qTox as a repository secret, and
the public portion is saved to qTox/doxygen as a deploy key.
This commit takes the existing travis task list and attempts to split
it into multiple jobs for the sake of efficiency. Also properly
separates out the build/deploy of documentation.
This commit enables travis to automatically build doxygen documentation
on updates to the master branch. The documentation is accessible from
the qTox website under the URL: https://qtox.github.io/doxygen