WIP Starting to work on IPython support for pydy.viz

This PR is created to implement IPython notebook support for visualizations. 
1. Looking up above, at line 303, it looks like the variable is `self.constant_values`. Are `self.constant_values` and `self._constant_values` different?
2. How are these used when the user invokes the next integration? How does the user run the next integration? I suppose you are working on that now?