Don't define .name on Joint module

Hey.. I hit a problem using Joint with @avdi's display_case gem.

It's accessing the name of classes like this: object.class.ancestors.map {|c| c.name}, which caused problems with the definition of self.name on the Joint active concern (as it takes a parameter).

All I've done here is move the utility methods like self.name and self.type and self.size to their own module.

It may well make sense to rename the .name method as well, as it's probably bad form.

Cheers, and thanks for all your awesome open source software!