fix typo, must be 'classifier' to appear on pypi.python.org
fix typo, must be 'classifier' to appear on pypi.python.org

The classifier info does not appear on pypi.python.org because of
the extra 's':  https://pypi.python.org/pypi/python-jenkins

Change-Id: Ifc58b8ded6ff8af077670051d7c3ca81fd7fc9f5

stackforge/python-jenkins,yershalom/python-jenkins,klmitch/python-jenkins,Puneeth-n/python-jenkins