Upgrade commons-validator to latest version (1.5.1)

Author: rpalcolea

grails-validation/build.gradle

@@ -1,5 +1,5 @@
 dependencies {
-    compile( "commons-validator:commons-validator:1.4.1" ) {
+    compile( "commons-validator:commons-validator:1.5.1" ) {
         exclude group: 'xml-apis', module:'xml-apis'
         exclude group: 'commons-digester', module:'commons-digester'
         exclude group: 'commons-logging', module:'commons-logging'