Update to json-ld.org playground for new syntax changes (@id, @type, etc)

The json-ld.org playground (http://json-ld.org/playground/) has been 
updated with the latest JavaScript implementation of JSON-LD 
(https://github.com/digitalbazaar/jsonld.js).

This update includes several syntax changes, including the new type 
coercion syntax, merging @subject and @iri to @id, merging @type and 
@datatype to @type, and removing @vocab and @base.

The C++, python, and php JSON-LD processor implementations were also 
updated to reflect these changes. These are linked to on the main 
json-ld.org page.

-Dave

-- 
Dave Longley
CTO
Digital Bazaar, Inc.