Enum and Bounded

[chris-martin]

This lesson covers the Enum and Bounded classes.

There are not a whole lot of exercises on this one, because there's a pretty limited scope of what you can do with these classes.

I included deriving-via and the generic-data package, in a "don't worry about how this works, but here's how you do it" presentation -- perhaps a bold choice, but it nicely fills in the gaps in GHC's stock deriving capability with little fuss, and I'm personally of the opinion that it's time to start talking about via as a normal thing to use.

[Kleidukos]

I agree with the normalisation of Deriving Via