Android gradle plugin 0.9.+ -> 0.11.+

This is to match the recent android studio ugprade 0.5.x -> 0.6.x as noted [here](http://tools.android.com/recent/androidstudio060released).

gradle_plugins/src/main/groovy/org/ros/gradle_plugins/RosAndroid.groovy

@@ -26,7 +26,7 @@ class RosAndroidPlugin implements Plugin<Project> {
                 mavenCentral()
             }
             dependencies {
-                classpath 'com.android.tools.build:gradle:0.9.+'
+                classpath 'com.android.tools.build:gradle:0.11.+'
             }
         }
         /**********************************************************************