Add configuration for change the size of the gutter marks

I refactored the existing color configuration to be a general settings window where you can configure your colors and set the gutter marks size. It looks like this.

![screen shot 2014-09-26 at 09 22 59](https://cloud.githubusercontent.com/assets/57446/4417087/1e0fbada-454e-11e4-9b09-6baaf65c979c.PNG)

When using the verbose options, the marks look like this

![screen shot 2014-09-26 at 09 22 47](https://cloud.githubusercontent.com/assets/57446/4417089/2e2c6314-454e-11e4-91b5-ac13b3182883.PNG)