Introduce object_rec() type (tupe()) and use it

Correct return spec for fetch/2
Inline fetch_sandbox and remove fetch_object helper now unused
Add missing object_rec() spec for delete
Move behavior based function to top in alpha order
Change signatures of delete and list to match chef_db functions

The pattern is: (object_rec(), #context{}, ...)
The rationale is that in chef_object, we will always want the object
record to be the first argument since we dispatch on it (although this
isn't strictly required). But having some sort of reason seems
helpful, so we'll go with that.

This is a backwards incompatible change and will require users of
chef_db to adjust signatures for those calls.
Restore node integration test
Fix dialyzer return spec for chef_db:list
Merge pull request #43 from opscode/sf/unify-sigs

Unify new behavior based functions and dialyzer fixes