avoid error with no content in Gson deserialization
adding test to gson deserialization with no content
removing wrong @Overrides used for interface
gson deserialization with resource method with many params
a json will be considered without root if there isn't any json root parameter with same name of resource method parameters
refactoring on empty string check
Merge pull request #536 from nykolaslima/gson_deserialization_with_resource_method_with_many_params

gson deserialization with resource method with many params (json without root)
Merge pull request #535 from nykolaslima/gson_deserializer_without_root

avoid error with no content in Gson deserialization