Enable a name remapping feature, remap plural models to singular

* Development happening at https://github.com/WP-API/client-js

Full changeset: WP-API/client-js@22b1e42...master

Props: @delphinus35, @adamsilverstein, @westonruter

Change highlights:
* Api builds models and collections from Schema, no hard coded models or collections; any endpoint in the schema will be mapped; supports multiple schemas (apis); helper methods for post model: all helpers user _embed data if available, otherwise using ajax request.
* new: Async load of api, apps can use the deferred to time startup
* new: Ability to localize schema, falls back to making an ajax request & cached in session storage; develop branch of client js has code that only localizes data once per session
* new Helper methods for Posts model: getCategories and setCategories
* fix: cleanup TimeStampedMixin
* new: models/collections get defaults and options from schema
* fix: all code up to WordPress JavaScript coding standards
* new: helper method to get post author user model `getAuthorUser`
* new: helper method to get a featured image for a post: `getFeaturedImage`
* new: models protect methods based on endpoint methods (eg. destory is blocked if an endpoint doesn't have a 'DELETE' method)
* new: models contain a reference to the original route object
* Ensure getters always return promise
* Add remapping for names, see WP-API/client-js#75
* additional helpers: add getMeta, getTags, getRevisions #76
* When SCRIPT_DEBUG off, use minified script; update localized data

* Development happening at https://github.com/WP-API/client-js

Full changeset: WP-API/client-js@22b1e42...477a49f

Props: @delphinus35, @adamsilverstein, @westonruter

Change highlights:
* Api builds models and collections from Schema, no hard coded models or collections; any endpoint in the schema will be mapped; supports multiple schemas (apis); helper methods for post model: all helpers user _embed data if available, otherwise using ajax request.
* new: Async load of api, apps can use the deferred to time startup
* new: Ability to localize schema, falls back to making an ajax request & cached in session storage; develop branch of client js has code that only localizes data once per session
* new Helper methods for Posts model: getCategories and setCategories
* fix: cleanup TimeStampedMixin
* new: models/collections get defaults and options from schema
* fix: all code up to WordPress JavaScript coding standards
* new: helper method to get post author user model `getAuthorUser`
* new: helper method to get a featured image for a post: `getFeaturedImage`
* new: models protect methods based on endpoint methods (eg. destory is blocked if an endpoint doesn't have a 'DELETE' method)
* new: models contain a reference to the original route object
* Ensure getters always return promise
* Add remapping for names, see WP-API/client-js#75
* additional helpers: add getMeta, getTags, getRevisions #76
* When SCRIPT_DEBUG off, use minified script; update localized data