Changed signature of ParameterizedFunction.instance() to match signature of Parameterized.__init__(). ParameterizedFunction.instance() no longer accepts *args, and no longer erroneously passes *args to Parameterized.__new__(); see #48.
Merge pull request #49 from ceball/fix_parameterizedfn_new_args

Changed signature of ParameterizedFunction.instance() to match signature of Parameterized.__init__()