Make AppVeyor badge target master branch
.. image:: https://img.shields.io/travis/cherrypy/cherrypy/master.svg?label=*NIX%20build%20%40%20Travis%20CI
:target: http://travis-ci.org/cherrypy/cherrypy
-.. image:: https://img.shields.io/appveyor/ci/jaraco/cherrypy.svg?label=Windows%20build%20%40%20Travis%20CI
- :target: https://ci.appveyor.com/project/jaraco/cherrypy
+.. image:: https://img.shields.io/appveyor/ci/jaraco/cherrypy/master.svg?label=Windows%20build%20%40%20Travis%20CI
+ :target: https://ci.appveyor.com/project/jaraco/cherrypy/branch/master
.. image:: https://img.shields.io/pypi/pyversions/cherrypy.svg
