Major update: OOP and more!

I took some time to learn how OOP works in Python, and as such I thought
it would be appropriate to convert most of my functions to classes. The
result is much cleaner and, in my opinion, much easier to read.

There is a superclass called DirObject that, as the name implies, turns
directories into objects. From there, each backup routine is placed into
its own subclass, complete with its own looping routines.