atom-python-isort leaves behind abandoned status bar item

[arl-o]

Running atom-python-isort successfully leaves behind a "isort: ✓" status bar item, which provides no additional information to the user once isort has run.

Since the status bar is generally used for important, persistent information (such as filename, language, interpreter, etc) I recommend that the status bar icon be removed entirely, and that errors only be displayed using the more canonical 'atom.notifications'.

As with #34, I'd be happy to update the package if nobody else is interested.

[lexicalunit]

Personally I prefer the status bar notification. This package works similarly to a linter for me so I just need the status update and then I run the command manually. Having a notification popup in the top right hand corner of my editor would be a distraction. I can imagine this would be a useful option though, for people who want it!