getElement() now uses O(1) get from hash instead of linear O(n) search. Enables us to read large files easily.

public/java/src/org/broadinstitute/sting/gatk/walkers/diffengine/DiffNode.java

@@ -107,11 +107,13 @@ public class DiffNode extends DiffValue {
         return getElements(false);
     }
 
+    /**
+     * Returns the element bound to name, or null if no such binding exists
+     * @param name
+     * @return
+     */
     public DiffElement getElement(String name) {
-        for ( DiffElement elt : getElements() )
+        return getElementMap().get(name);
-            if ( elt.getName().equals(name) )
-                return elt;
-        return null;
     }
 
     /**