Feature kiitos received

- Different text color when the current user sent the kiito
- When the current user sent the kiito it displays 'by Me' instead of the user name
- When the kiito was sent today, it displays 'Today' instead of the formatted date
- Extracted the messages haml code to a partial
- Created a message decorator for the front end formatting
- Minor styles formatting
- Ignore uploaded images in dummy app
- Remove presence validator and test for the 'to' property in message model