Ert tests for files within the "tests" directory

This automates the testing of files in the `tests` directory. Currently, issues 9, 14, and 19 fail under `GNU Emacs 24.2.1 (i686-pc-linux-gnu, GTK+ Version 2.20.1) of 2012-09-05`, so they are marked as expected failures so that all tests pass. Once the underlying bugs are fixed, the expectation of failure should be removed.

This closes ejmr/php-mode#60