Inflector rules

[fsmanuel]

@corrspt reported emberjs/ember-inflector#91

I did some digging and found an inconsistency in the way we use pluralize.
Sometimes we use Ember.String.pluralize (here and here) and in the serializer we import from ember-inflector (here).

It seems that they use different instances. Ember.String.pluralize doesn't use the new inflection rules.

related #3802, #3730

[fsmanuel]

as i posted in slack:

// inside an app:
console.log(Ember.Inflector.inflector);
// => ember$inflector$lib$lib$system$inflector$$Inflector

// inside ember data
console.log(Ember.Inflector.inflector);
// => Inflector

[fivetanley]

fixed by #3888