add tests for CrudServiceImpl and add arguments validation for findAll(PageRequest) and findByIds methods. fixes #233
add tests for JpaExceptionHandler
refactor JpaHandlerException
refactor JsonValidationControllerIntegrationTest, add @JsonCreator constructor on ModelConstraint.java
add mocked ValidationControllerTest
add basic unit test for RepositoryBasedRestController
add basic unit test for ServiceBasedRestController
add test for ResthubExceptionhandler and refactor
Merge pull request #234 from bmeurant/master

some work on tests