Update I-JSON reference

Update I-JSON reference from (OLD): [I-JSON] Bray, T., Ed., "The I-JSON Message Format" draft-bray-i-json-01, 06 January 2014. http://tools.ietf.org/html/draft-bray-i-json-01 to (NEW): [RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493, March 2015. https://tools.ietf.org/html/rfc7493 also add text like the following to the description that includes the DateTimeOffset and TimeOfDay values in section 7.1 Primitive Value The DateTimeOffset and TimeOfDay data types as defined in [OData-ABNF] allow for the seconds component to be omitted. For compatibility with [I-JSON] , OData clients and servers SHOULD include the seconds component.