added patch visibility and axis visibility props

In order to make twinx and/or twiny working with the latest version of matplotlib, we need to pass on the visibility of the patch. For completeness, I also pass on the visibility of the axis given that twinx/twiny also modifies this.  
It looks like you are sneaking in a few additional tests here.  Can you add a note about it?  Or is this actually related to the visability props and I'm just confused?