Small performance improvement.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1549094 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/math3/genetics/Chromosome.java

@@ -59,7 +59,7 @@ public abstract class Chromosome implements Comparable<Chromosome>,Fitness {
      * </ul>
      */
     public int compareTo(final Chromosome another) {
-        return ((Double)this.getFitness()).compareTo(another.getFitness());
+        return Double.compare(getFitness(), another.getFitness());
     }
 
     /**