Add level analysis tool and path support

"Level analysis tool": meant for programmers, not average users.

It's a loop that opens every NSMB2 level. You can then add code to other
parts of the editor to gather information. Tip: use the new global
variable "CurrentLevelNameForAutoOpenScript", which (when the
auto-opening loop is enabled) will always contain the name of the level
currently being opened.
You need to change the AutoOpenScriptEnabled variable to True within the
source code for this to work.

Path support: Reggie now supports NSMB2 paths. That's about it.

There are also a few minor bug fixes included.
Removed a print statement

I missed one. :P

(And yes, print is technically no longer a statement in Python 3. It
just sounded wrong to say "removed a print function".)
Add Grop's tileset name list

Thank you to Grop for creating this great list of New Super Mario Bros.
2 tilesets!
Change spelling of a reggie.py variable

Hooray for American spelling!
Add contributors to the readme

Large changes to the Developers section of the readme to disambiguate
who worked/is working on what game, and added the NSMB2 researchers and
contributors.