Added anchors to headers in documentation

@harvesthq/chosen-developers We can now give people links to the sections in the documentation to help answer their questions.

![image](https://f.cloud.github.com/assets/127289/849176/be93d710-f46f-11e2-8355-a905fe56ef84.png)

@starzonmyarmz Could you give me a hand to replace the 'link' text with a nice icon?

**Open Issues**

- [x] Add anchors to documentation pages
- [x] Replace link text with icon
- [x] Decide if we want icon to always display or only on hover