Create a panel similar to Brackets linter panel

@MiguelCastillo Will comment on a few places in code later, but wanted to get this out there for you to review.

Fixes #68.
I would setup the template to have an attribute more like `<tr data-linenumber={{line}}>`.  Classes should mostly be used for styling.  So, this event handler can then change to `"click", "[data-linenumber]"`.  The calback's `this` context will be the element you clicked, there is no need to get the target from the the event.