Added new Block structure to replace ints and bytes.

Passes existing tests, need to look at whether individual structs need tests.
Started the blocklist and wrote a test for it.

The test passes.  Woo!
Added block data!

I've added very little more than the limited subset of functionality
that this project requires.  Pull requests with improvements would be
appreciated!
Forgot to fix the broken tests...

Forgot to change the comparison when I changed the data types.  Better now!
Updated TODO with progress.

Now to move on to the maps...