API: Add a `KineticModel` method to handle cycle and diagram plotting

[nawtrey]

As discussed in 3. of this comment, the structures of plotting.draw_diagrams() and plotting.draw_cycles() are very similar. It shouldn't be terribly difficult to combine these into a single plotting function that can handle both kinds of figures. This is probably best handled after the completion of #47.

[nawtrey]

One thing that would help with this is to add a parameter**params to _plot_single_diagram() instead of manually specifying every single input parameter we want to use since a host of them are only used for inputting directly into NetworkX plotting functions. It would also simplify the documentation substantially, which would make things much more concise. This should probably be handled first, and detailed in a separate issue.

[nawtrey]

With GH-83 merged, I think this can be refocused on adding a method to the new class object.