adds logic for running focussed shoulda test

[eellson]

This checks for a shoulda test case if we don't find a standard test for
the present loc.

This approach is likely flawed, however:

• We presently use the filename for deciding what sort of test to run, and
  we will not know whether using shoulda or not at this stage.
• I do not expect this to get merged in seeing as the project looks
  pretty inactive.
• I think it's worth putting here so others can use regardless.

[jgdavey]

Thanks!