Add a lint indicator that replaces Brackets lint indicator

Removes default Brackets lint status indicator.
Replaces the `errorIndicator` with this `lintIndicator`.

See #61 for more detail on the reasons for this. 
I'm going to rework this soon to use transitions and not animations, but I would still need to remove the class at some point. One alternative is to simply do something like this:
```
$statusBarIndicator.removeClass("pulse");
$statusBarIndicator.addClass("pulse");
```

which *should* work.