add links to soulmates and jobs to the top nav

The links to Jobs and Soulmates are added to the top nav, for tablet and bigger screens. No changes on mobile.
Feature behind the switch: 'guardian-services-links'

![services links](https://cloud.githubusercontent.com/assets/1492162/3569417/2056a7e8-0b3f-11e4-8240-fadb7707a835.png)
![screen shot 2014-07-14 at 10 42 06](https://cloud.githubusercontent.com/assets/1492162/3569418/207ca772-0b3f-11e4-8c26-df04673b05e4.png)

![](http://media.giphy.com/media/43VhxnrEOQ44U/giphy.gif)