Support for additional links in header (closes #87)

:dancer: Adds support for custom header links. :dancer: 

:star2: Supports automagic hyperlink creation and multiple dd's values for each key. 

Example of what it looks like:  

![Screen Shot 2013-04-28 at 22 44 02](https://f.cloud.github.com/assets/870154/436440/cac293ee-b04c-11e2-94c4-6687e16b5e72.png)

New property "otherLinks", and example: 

```JS
otherLinks: [{
      key: "Repo",
      value: "We are on Github",
      href: "https://github.com/darobin/respec"
  }, {
      key: "Bug tracker",
      href: "https://github.com/darobin/respec/issues?state=open"
  }, {
      key: "No linking",
      value: "I don't hyperlink."
  }, {
      key: "Previous Editors",
      data: [{
              value: "John Smith",
              href: "http://example.com"
          }, {
              value: "Adam Smith"
          }, {
              value: "Foobar Smith"
          }
      ]
  }
]
```

Note: I'm not 100% happy with the names of the properties I used, but if you guys are ok with them, I can live with them.