Replace 'Werkzeug' to 'Flask'

CONTRIBUTING.rst

@@ -56,9 +56,9 @@ Then you can run the testsuite with::
     py.test
 
 With only py.test installed, a large part of the testsuite will get skipped
-though.  Whether this is relevant depends on which part of Werkzeug you're
-working on.  Travis is set up to run the full testsuite when you submit your
-pull request anyways.
+though.  Whether this is relevant depends on which part of Flask you're working
+on.  Travis is set up to run the full testsuite when you submit your pull
+request anyways.
 
 If you really want to test everything, you will have to install ``tox`` instead
 of ``pytest``. Currently we're depending on a development version of Tox