Fixed issue #771.Comment allow new line.

Raising Fresh PR on issue #771 as my previous branch got messed up while pushing from local.
I have tested all scenarios from my end. 
The comment div is taking care of next line.
In case of edit it accepts new line and on hitting enter it goes to next line. to post the changed comments user will follow same ctrl+enter.
It seems strange to add the border when enter is pressed.  If you think it should have a border while it's editing then you should add it when editing starts and remove it when editing stops.  Same goes for the minimum width - it doesn't really have anything to do with pressing enter.  If it needs a minimum width then either the element should always have a minimum width from when it's created, or one should be added when starting editing and removed when editing finishes.