Include MITLM as a submodule

[eddieantonio]

Submodules suck, but it might be beneficial to include our own version of MITLM as a submodule. This will make continuous integration easier (#9), and might make the install instructions easier, i.e.:

$ apt-get install libzmq gfortran # etc.
$ git clone --recursive  https://github.com/orezpraw/unnaturalcode.git
$ # cd, make, source this, test

Of course, whether the effort of will be worth it, considering work on UnnaturalGrams has already been started, is another thing.