Add travis test runner; update dependencies.

Note that the version of XeLaTeX is very old; we need to update the
hyperref package (and the ltxcmds package it depends on) and the
fontspec package.  Note that the new fontspec installation needs to be
moved from 'latex' to 'xelatex' to properly override the default
xelatex fontspec.

Change-Id: Ic8647430bd2f6255b1d3efb8b0313741047d2876