`tests` should be `test` in README

[kmicinski]

Kyles-MBP-2:jeeves micinski$ nosetests tests/gallery/authentication
E
======================================================================
ERROR: Failure: OSError (No such file /Users/micinski/projects/jeeves/tests/gallery/authentication)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Library/Python/2.7/site-packages/nose-1.3.7-py2.7.egg/nose/failure.py", line 42, in runTest
    raise self.exc_class(self.exc_val)
OSError: No such file /Users/micinski/projects/jeeves/tests/gallery/authentication

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (errors=1)
Kyles-MBP-2:jeeves micinski$ nosetests test/gallery/authentication
....
----------------------------------------------------------------------
Ran 4 tests in 0.050s

OK