Correct key bindings for alt keyboard layouts

This fix uses the Unicode Utilities to check what letter is produced by
each key code in SDKeyBindingTranslator's initialize method. The values are
then stored in a NSMutableDictionary that is later used to check for the
proper key code for single character bindings. Only the subset of key codes
that can produce different characters for different keyboard layouts are
checked.

I encountered this bug because I use a Dvorak layout, and the keys in my config
didn't correspond with what I was expecting (instead they mapped to the physical
keys).

Also, I was working with Xcode5-DP, and there were a few small fixups required
in order to get everything to build. I've included them with this pull request.