Merge pull request grails#1 from nvaidyan/master

Update select tag docs to show what else optionKey/optionValue can do

src/en/ref/Tags/select.gdoc

@@ -77,6 +77,14 @@ If you require even more control over how each @<option>@ element is presented t
           name="book.title" from="${bookList}" />
 {code}
 
+This can work nicely for when you want to pre-select a value from the list on form load. 
+For example, assume we are passing in a @favoriteBook@ variable corresponding to an object in the @from@ which should be pre-selected. 
+
+{code}
+<g:select optionKey="id" value="${favoriteBook.id}"
+          name="book" from="${bookList}" />
+{code}
+
 h2. Source
 
 {source:tag=FormTagLib.select}