Implement LevelModel and LevelPresenter

[s2saba]

The LevelModel class should have a reference to the contents of the text file. It should also keep track of the state of each character (untyped, correct, incorrect, bad form). The LevelPresenter class should expose a subset of these characters to the view. As each character is typed, the 'character window' is shifted one place to the right. Furthermore, each character state should be translated into a character color that the view can then use.

[eh-dub]

Awaiting testing by me.

[eh-dub]

Still needs yellow characters (incorrect form) which requires connection with the prototype.