Icon fix on OSX 10.8 and other improvements

The icon was not loading on OSX 10.8, not quite sure why, but a combination of the `file://` protocol and a check for _localhost_ in [ruby_gntp](https://github.com/snaka/ruby_gntp/blob/master/lib/ruby_gntp.rb#L270) breaks it (see: snaka/ruby_gntp@e84809d3c89bf444845baeba25550a89ff37a0a6). It's a bit of a hack but I was able to avoid this by instantiating GNTP using `127.0.0.1`.

While at it I made a few improvements:
- Proper application name
- Better title, this also allows for more characters to be shown on errors
- Sticky for errors (inspired by the compass doc)
- New icon :)
- Finally, there was an error with the constant used for the init, it's fixed