Add functionality for graphing area under plot (integral)

[tekktrik]

1. Adds the ability to plot the area under the curve (integral)
2. Minor documentation tweaks and cleanup

[FoamyGuy]

@tekktrik thanks for working on this new functionality, would you be interested in adding an extra example that shows the usage of this new feature?

[tekktrik]

Sure thing! I'll throw together an example file :)

[tekktrik]

Added new example file for simulating dice rolls and plotting the distribution - uses this new functionality!

[tekktrik]

@FoamyGuy just checking in on some of my older PRs and wanted to check if there's anything else that needs to be done!

[FoamyGuy]

Thanks for the reminder, I lost track of this one.

Looks good to me. Tested the new example successfully on PyPortal.