Error status indicator.

Hi, I admittedly thrown this together in a little time so it may not be as good as it is required for a merge request, but I sorely miss the feature it provides: it shows to the user if the compilation was ok without requiring her/him to open the developer console.

If it is indeed good enough to be merged it can be used to provide a nice place for invoking the error logs. By making the ErrorIndicatorView listening for clicks one can open a new editor page showing the error log. I'm willing to work on this if you think this is useful. 

By the way, thanks for the package. I surely hope it evolves fast to incorporate a number of neat features presents in other editors.