Clarify use of :

Author: josevalim

assets/js/handlebars/templates/search-results.handlebars

@@ -40,7 +40,7 @@
     <li>Use <code>*</code> anywhere (such as <code>fo*</code>) as wildcard</li>
     <li>Use <code>+</code> before a word (such as <code>+foo</code>) to make its presence required</li>
     <li>Use <code>-</code> before a word (such as <code>-foo</code>) to make its absence required</li>
-    <li>Use <code>field:word</code> to search on a particular field. The available fields are <code>title</code> and <code>doc</code></li>
+    <li>Use <code>:</code> to search on a particular field (such as <code>field:word</code>). The available fields are <code>title</code> and <code>doc</code></li>
     <li>Use <code>WORD^NUMBER</code> (such as <code>foo^2</code>) to boost the given word</li>
     <li>Use <code>WORD~NUMBER</code> (such as <code>foo~2</code>) to do a search with edit distance on word</li>
   </ul>