Adds tests to the repository

It has taken some time, but this is a full test suite for The Good Suite.

It has full coverage except for:

- Error paths aren't being tested yet (#22 should change that)

- A skipped test in GoodLooking causes some other tests to be skipped,
  which causes a lack of coverage in some very simple cases of a switch.
  The culprit is #29

- str_replace_once from GoodLooking (Regexes.php) isn't fully tested,
  especially the recursive parts of that function. They are never used and
  that part of the compiler needs an overhaul anyway.

This closes #2.
Added a quick Exception to wrong code branch

This used to return an empty string, but it seems this was an artifact
from a bygone era.