composable kwarg iterator (Python 3)

 When using matplotlib and plotting more than one line, it is common to want to
 be able to cycle over one or more artist styles; but the plotting logic can
 quickly become very involved.
 .
 To address this and allow easy cycling over arbitrary 'kwargs' the `Cycler`
 class, a composable kwarg iterator, was developed.
 .
 This package contains the Python 3 version of Cycler.