Temporary fix for mongoose bug

mongoose does not support Query.remove(condition,done) as noted in its
documentation. This is a temporary fix.
Made contextFilter async, Corrected delete status code

delete by id now returns 404 when no items are deleted
extracted function from duplicate code in createObject()
unstable: tests written for postCreate and postDelete
Added postCreate and postDelete

postCreate is run after a document is created. Passing a (truthy) error
to its callback will send a 400 status code (TODO is this correct?). A
falsy value resumes normal operation.

postDelete follows the same logic for deletion.
Merge branch 'master' of github.com:09setht/express-restify-mongoose into 09setht-master

Conflicts:
	lib/express-restify-mongoose.js
	test/test.js

fixed conflicts
updated documentation
bump version to 0.6.7