Add support for scopes

[Spone]

Close #11

[calebhearth]

I like it. Thanks. I'm curious whether we can chain scopes off of where.not? For example, does where.not.deleted work here?

I can check this myself later but if you're at a terminal and willing to try it out that may speed things up!

[Spone]

-          where.not("#{field}": nil)
+          where.not.send(field)

It works. Do you prefer this?

EDIT: or maybe you meant remove the not_#{attribute} scope altogether?

[calebhearth]

Yeah my thought is to not include the not_ scope, since it seems to be pretty easy to do in app code.

[Spone]

Fine. Let's rename the option scope (singular) then?

[Spone]

Hey @calebhearth let me know if there's anything else I can do to get this merged :)