Polishing:

* Upgrade JRuby to 1.7.12
* Replace `AnnotationFinder` with moving its methods to `MessagingAnnotationUtils`
* Refactor aggregator classes to use `MessagingAnnotationUtils` to determine the method for annotation
* Fix `IntegrationComponentScanRegistrar` to skip annotation classes
* Fix `MessagingGatewayRegistrar#replaceEmptyOverrides`
* Improve `MessagingAnnotationPostProcessor` to use `ReflectionUtils.USER_DECLARED_METHODS` `MethodFilter`
* Change the `MethodAnnotationPostProcessor` hierarchy to use just list of annotations to process attributes