Built In Type Extensions from MotionModel

Added Hash#empty? and Hash#except
Added inflector
Added nilclass extensions
Changed String#pluralize and String#singularize to use Inflector, added String#camelize, String#underscore, String#humanize, String#titleize, String#empty? and modified String#classify to return a real class instead of a string.
Added symbol extensions
Added array extensions
Added specs for the foregoing

Note that there is a different behavior for String#classify. It now actually gets the class and returns an object of type Class.