More pythonic interface

[perimosocordiae]

This is a big change, so feel free to take only the parts you like.

I converted the wrapper to a more "pythonic" interface by:

• exposing a lot of the simple methods as read-only properties
• simplifying the settings getters/setters
• renaming methods to snake_case
• making the data-filling functions a bit easier to understand/use

I updated the example programs to use the new API, so check out the diffs there to see how my changes affect usage.

The downside of all of this is that the new interface names are no longer a one-to-one mapping with the C++ ALE interface. The new names should hopefully make sense to someone who knows the C++ interface, though.