Updated JSON.swift for beta 5, tests are next.
Fixed .DS_Store exclusion.
Module name changed from JSON to JSONLib to avoid conflicts in type usage.
Significant refactoring, including JSON* renamed to JS*; the names just felt more natural.
Proper handling of the error case for unsafe integer values for communicating with JavaScript.
Added Error and Failable/FailableOf to better represent error states.
Added convenience initializer for NSData encoded data.