Merge pull request #110 from w3c/ref_to_sparql

Added informative reference to SPARQL11-OVERVIEW in intro.

As suggested in #109

index.html

@@ -284,7 +284,7 @@ <h1>Introduction</h1>
   <p>
    JSON-LD is designed to be usable directly as JSON, with no knowledge of RDF
    [[RDF11-CONCEPTS]]. It is also designed to be usable as RDF, if desired, for
-   use with other Linked Data technologies like SPARQL. Developers who
+   use with other Linked Data technologies like SPARQL [[SPARQL11-OVERVIEW]]. Developers who
    require any of the facilities listed above or need to serialize an RDF <a>Graph</a>
    or <a>Dataset</a> in a JSON-based syntax will find JSON-LD of interest. People
    intending to use JSON-LD with RDF tools will find it can be used as another