Add UtopianEngine::PushScore()

Added UtopianEngine::PushScore(), which puts the score held in the
UtopianEngine into JavaScript for modification if desired. This will
facilitate using both UtopiaScript and JavaScript for score
modification.
Move width and height to Rooms node

Resolves #49
Add checkKeys() functions

Added the following functions:
KeyCombo::checkKey(String key)
Roomstate::checkKeys(String key)
Room::checkKeys(String key)

Set up UtopianEngine::run() and each of the aforementioned functions to
call one another appropriately.

Resolves #40.