implement getAdapter
update tests of default adapter to use getAdapter()
remove superfluous sanity checks, getAdapterForModel throws an error in any case if adapter is not found.
update EventedQueryProcessor constructor to use getAdapter() instead of straight model.adapter
Merge pull request #209 from moitias/getAdapter

This is awesome!

There's breakage in the build, but it's in Node v0.8, and looks to be the tilde/caret changes in the package versioning. I'll take a look at this later.

Thanks for knocking this out.
Merge branch 'master' of github.com:geddy/model into nested-eager

Conflicts:
	lib/adapters/sql/base.js