Fixed the biggest memory issue. Remember how in your first computer
programming course your professor told you not to resize something while
iterating over it?  Yeah.

I got to chunk (11,11) without valgrind complaining (it took a while on
Lappy), which would indicate that the vector resizing is working right.

Stairs to dungeons still aren't connected properly. I haven't even
looked at it yet, but I'm not nearly as concerned.