Change way to run tests in readme

Author: jenshnielsen

README.rst

@@ -20,15 +20,17 @@ Testing
 
 After installation, you can launch the test suite::
 
-  python setup.py test
+  python tests.py
 
 Or from the python interpreter::
 
   import matplotlib
   matplotlib.test()
 
 Consider reading http://matplotlib.org/devel/coding_guide.html#testing for
-more information.
+more information. Note that the test suite requires nose and on python 2.7 mock
+which are not installed by default. Please install with pip or your package
+manager of choice.
 
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