Improved installation text.

Author: nicoddemus

docs/index.rst

@@ -28,6 +28,8 @@ The `pytest-qt`_ package may be installed by running::
 
 .. _`pytest-qt`: http://pypi.python.org/pypi/pytest-qt/
 
+This will automatically register ``pytest-qt`` for usage in ``py.test``.
+
 
 Tutorial
 ========