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).  In addition
XeLaTeX doesn't seem to honor the font path, so we need to put our
fonts in the system font path.

Change-Id: Ic8647430bd2f6255b1d3efb8b0313741047d2876