Revert "Remove Ember.String.classify from ember-inflector"

This reverts commit 4cd5434cfe1a6a3addc9e250be9b5f8b2c2f0461.
Upgrade libraries
Add a flag Ember.INFLECTED_CLASSIFY

Add a flag Ember.INFLECTED_CLASSIFY defaulted to false. If
Ember.INFLECTED_CLASSIFY is true, Ember.String.classify function from
ember-inflector will be used instead of Ember.String.classify function
from ember-runtime.