Promote ConstantResolver to own file
Refactor: push inflector down into strategy
Inflector requires model

The constant resolver is responsible for determining the model
Use ActiveModel::Name for some inflections

This fixes #77, but also introduces a breaking change.

Namespaced models previously used demodulize for their param_key for
attribute assignment. For example an Admin::Page model would assign
attributes based on params[:page]. The Rails convention is to include
the module as part of the param_key. Thus, Admin::Page would be assigned
from params[:admin_page].