no-brainer patch for Active Support

I am revising AS stuff in the framework while covering core extension for the AS guide.

There are class reopenings in Action Pack to add generic stuff like TrueClass#to_param whose natural place would be AS/core_ext in my view (where Array#to_param and friends live). Even Object#to_param is defined twice.

I've refactored them out to standard places in AS, and added test coverage which was lacking as well:

Totally +1.