Change chloropleth colours, fixes #45

Use red colours from http://colorbrewer2.org/

These are still in the brand, but stand out more on the map
and aren't as pale.

![map view table regionofbirth - wazi 2014-10-06 19-37-51](https://cloud.githubusercontent.com/assets/4178542/4530295/8ac8c778-4d7f-11e4-8e52-da0e5d97c203.png)