* added a condition to check if owner of the comment is in mentions
* added a test to check if comment owner can mention self
* fixed metion test by:
- adding a second user to simulate a owner of a comment
- change the user on comment to owned by newly created user
* Implemented ActiveJob for Mention#send_email_notification
* Implemented ActiveJob for Mention.create_all
* Fixed args while calling the job
* Changes as per the review