Use the Property options :messages from dm-validations if define

To change error message, you can do only by default overriding.
dm-validations add an option to property allow overriding this message.
This commit use it if it's define.
avoid some failure if no messages property define
Merge pull request #21 from shingara/features/allow_message_property_usage_on_error_message

Use the Property options :messages from dm-validations if define