Issue #6 and #10: Complete Travis CI integration

This pull request fixes both #6 (Fixing issues with Travis CI) and #6 (Fixing lingering test failures). It backported the modification to the l() function that removes calls to theme_link(), which unbelievably was causing the failure in the TablesortTest. Apparently unit tests that called l() resulted in theme layer getting initialized, but since unit tests don't have Drupal installed, the theme system initialization would cause a DB error. Backporting the patch to remove the theme call from l() seemed like the easiest fix (and good for performance too).