Use "http://www.w3.org/ns/json-ld#context" instead of "describedby" l…

…ink relation

This addresses #197.

spec/latest/json-ld-syntax/index.html

@@ -1476,7 +1476,7 @@ <h2>Referencing Contexts from JSON Documents</h2>
 <p>
 In order to use an external context with an ordinary JSON document, an author
 MUST specify an <tref>IRI</tref> to a valid <tref>JSON-LD document</tref> in an HTTP Link
-Header [[!RFC5988]] using the <code>describedby</code> link relation.
+Header [[!RFC5988]] using the <code>http://www.w3.org/ns/json-ld#context</code> link relation.
 
 The referenced document MUST have a top-level <tref>node definition</tref>. The
 <code>@context</code> subtree within that object is added to the top-level
@@ -1502,7 +1502,7 @@ <h2>Referencing Contexts from JSON Documents</h2>
 HTTP/1.0 200 OK
 ...
 Content-Type: ****application/json****
-****Link: <http://json-ld.org/contexts/person.jsonld>; rel="describedby"; type="application/ld+json"****
+****Link: <http://json-ld.org/contexts/person.jsonld>; rel="http://www.w3.org/ns/json-ld#context"; type="application/ld+json"****
 
 {
   "name": "Markus Lanthaler",
@@ -1516,7 +1516,7 @@ <h2>Referencing Contexts from JSON Documents</h2>
   served with the <code>application/ld+json</code>
   media type MUST have all context information, including references to external
   contexts, within the body of the document. Contexts linked via a
-  <code>describedby</code> HTTP Link Header MUST be ignored for such documents.</p>
+  <code>http://www.w3.org/ns/json-ld#context</code> HTTP Link Header MUST be ignored for such documents.</p>
 </section>
 
 <section>