Fix compatibility with activerecord 4.1.2.rc1

where_values_hash now taskes the reflection name as an argument, so we
need to update the monkey patch. This should be fully backwards
compatible.
remove with_required_attributes scope

because i get the missing attributes via fallback
Merge pull request #354 from felixbuenemann/rails-4.1.2.rc1-compatibility

Fix compatibility with activerecord 4.1.2.rc1
removed with_required_attributes completely
Use reflections or _reflections, whichever is defined.

Not beautiful, but this should fix #353 for now. Also see
rails/rails#15300.
Added Gitter chat option

[CI skip]
Refactor using reflections class method.

Via @vuvanly in #357.
Update changelog and readme.
Release 4.0.2.
Merge branch 'patch-1'