Add Status Item icon

Hi! Really liked this tiny project. :smile: 

Here are my 2¢: I feel like having an icon instead of "SSH" on the status bar goes more in line with the other status bar apps for OSX, so I added this. It also makes the app feel more "general purpose" in the sense you might want to add commands to the JSON file that are not just SSH. (Like start/stop server, etc)

Here's what it looks like:

![](http://i.cloudup.com/BBCQLnBELq.png)