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'

![png](https://cloud.githubusercontent.com/assets/1492162/3597483/6386a1aa-0cd2-11e4-9438-e0a8d0d9e842.png)
![screen shot 2014-07-16 at 11 15 04](https://cloud.githubusercontent.com/assets/1492162/3597484/63b0c00c-0cd2-11e4-9d5a-f0e459b6cef7.png)
Mobile -- unchanged
![screen shot 2014-07-14 at 10 48 07](https://cloud.githubusercontent.com/assets/1492162/3569758/89e3a53a-0b44-11e4-9114-7b8fcddf4098.png)

![](http://media.giphy.com/media/43VhxnrEOQ44U/giphy.gif)
We should keep these variables in their module so that it's easily portable.