Updating module namespace.

Adding package module imports to `pymsbayes.__init__.py`.
Adding `NumberOfDivergencesSummary` to `parsing`.

Adding `NumberOfDivergencesSummary` class to `parsing` module.  The
class summarizes results for the number of divergence events.
Updating plotting module.

Adding `BarData` class and incorporating it as an attribute of
`ScatterPlot` class.