* Implement `links` via optional interfaces
* Updating example app to include links
* Update readme with links information
* Exclude a slice relationship only if the slice is empty AND there are no defined links
* Remove `Link` in favor of vanilla `map[string]interface{}`. More flexible for different allowed links spec implementations.
* Update app.go with correct Links methods
* Use LinksObject and LinkObject types along with type assertion to provide errors when marshaling an invalid links JSON API object.
* Renamed LinksObject Links and LinkObject Link
* Added back the relationship link post merge.
* Renamed the JSON* Linkable functions JSONAPI* such that when a library user implements the interface it is clear the functions are used for JSON API as opposed to JSON
* Example cleanup.
* Refactor the example to use constants from jsonapi and http.
* Add support to nullify relationship; http://jsonapi.org/format/#document-resource-object-linkage
* Fixed: [null] is not valid as an empty relationship.
* add support for 'omitempty' on relationships; default behavior of marshalling empty/nil relations (i.e. w/o 'omitempty' tag) marshals with null data relation
* cleanup whitespace
* Added go 1.7 to test versions; fixed the marshaling of empty relations to return an empty array rather than a null/nil. Added a more robust test case for the marshaling of non omitted relations.
* Cleanup.
* Added a comment to UnmarshalMany
* Document the ‘omitempty’ annotation on a relation.
* Add common JSON API values as exported jsonapi pkg constants.
* add support for direct use of slice of struct pointers for MarshalMany
* Added a test to ensure that whether MarshalManyPayload is called with a []interface{} or []*Struct it will produce the same desired result.
* Added a test to show how the new error type may be returned.
* Ensure the outside accessible Errs have comments.
* Page char width cleanup. Addressed warnings about duplicated "client-id" definition; using the const.