First cut at functioning Roles.

Don't think this is the ideal approach but works for the simple case.
Fix method composition for Roles.

So now the appropriate method is used so methods are composed like
regular ruby code.
Add a test for multiple roles.

A sanity check mostly and should hopefully catch silly bugs that I'm
likely to introduce.
Add build_all + build.

Which has already revealed limitations but the gist works - calls build
at the end of initialize for all parents down to the invocant's class.
Compose all attributes up the inheritance chain.

It seems like inheriting class behaviour in addition to attributes would
be useful. Ahem. And move attributes tests into its own spec file.