Add Map/World stuff
Fix map loading (#6)

Several issues that I had fixed before, but didn't tell myself how I
fixed them.  I couldn't manage to force an image depth of eight bits
with ImageMagick or Preview (for OSX), so using ImageMagick I set a
slight blur on the tile set to force the correct depth.  (Apparently, it
will default to the lowest depth that maintains image integrity.  Since
it was only black and white, monochrome worked well enough.)