Test Database Upgrades using Travis

[preaction]

The DBIx::Class::Schema::Versioned upgrade files (located in share/) need to be tested somehow. Since it's a bit onerous to make all developers install a local MySQL and keep it running, it'd be nicer if Travis could do it.

We need to install MySQL on Travis, install the 0.000 version of the database, and then run it through the upgrades. In theory, simply using bin/cpantesters-schema install should do it. If it fails, we'll have the output needed to diagnose the problem.