Changes in this commit: WP-API/client-js@0d01ff4...master

• Support lodash, plus older and newer underscore: add an alias for _.contains
• Add args and options on the model/collection prototypes
• Rework category/tag mixins to support new API structure
• Add workaround for the null/empty values returned by the API when creating a new post - these values are not accepted for subsequent updates/saves, so explicitly excluding them. See Post endpoint - remove empty/null values from the return data. #2393
• Better handling of the (special) me endpoint
• Schema parsing cleanup
• Introduce wp.api.loadPromise so developers can ensure api load complete before using