Load resources as array of bytes

This would be particularly useful when loading fonts, added the three specific platform implementation and wrote a simple unit test for it.
I don't think realpath will help; the issue isn't symbolic links or anything, it's that we don't know exactly where the current directory is relative to resources (but the foundation functions do, somehow).

You're right though, it's kinda bad to never `release` the NSData object. Even though we'll deallocate the data that it's wrapping, we'll probably leak a few bytes from the object itself. 

Maybe we can do something clever with the bridged `CFData` type, since CF types aren't reference-counted. I'll read a bit on this.