Update MysticMine to python3

[mic47]

Since python2 is being onset, it will be harder to install this game on newer systems, so it might be good idea to convert ti to python 3, as I tried to do that in this PR.

What I did: 0. Change pyrex to cython (literarly just change the import and it worked).

1. I run 2to3 to convert most of the code.
2. Then I fixed the imports.
3. Then I went through al uses of division, and change to integer division where appropriate (before that, there were bunch of graphic glitches or crashes). This is probably the change that needs most careful eye during code review.
4. _ was undefined, defined it to gettext.gettext

Testing: I run unittest, and while I didn't finish the game yet with this version, but I unlocked all but one items and game seems to work.