setting up unit testing for javascript
Altering the header js module to be a dough component

- Remove need to call init on header module as it
  will be initialised by componentLoader now
- added lots of dough data attributes to markup which
  reduces the amount of config in the Header.js file
- altered the way to work out whether the user is seeing
  the shallow version of the header by adding an
  :after psuedo element which is read by the JS
- Adding very basic initial unit test for header component