Clarify that language map values of @none are strings, and not aribrary data.

Fixes #102.

Author: gkellogg

index.html

@@ -6009,8 +6009,8 @@ <h3>Using the Document Base as the Default Vocabulary</h3>
 
   <p class="changed">If the <a>processing mode</a> is set to <code>json-ld-1.1</code>,
     the special index <code>@none</code> is used for indexing
-    data which does not have a language, which is useful to maintain
-    a normalized representation.</p>
+    strings which do not have a language; this is useful to maintain
+    a normalized representation for string values not having a datatype.</p>
 
   <aside class="example ds-selector-tabs changed"
          title="Indexing languaged-tagged strings using @none for no language">