Outside gauge

@mmorey Review.

![ios simulator screen shot jul 31 2014 2 00 05 pm](https://cloud.githubusercontent.com/assets/246403/3771518/e693aaaa-18f5-11e4-959b-726c528ed08d.png)

Implementation of issue https://github.com/chaione/CHCircleGaugeView/issues/21

Also fixes issue https://github.com/chaione/CHCircleGaugeView/issues/33