feat(main.js): Prototype String Obfuscation, Input Filtering & Binding

* Obfuscates the regPlate & stockRef whenever the two are long enough to be
  processed (regPlate must be >= 3 characters, stockRef must be >= 9 characters)
* The capitalize directive capitalizes the data entered into the input fields.
  This goes further than the standar angular.uppercase, which merely changes how
  the input is presented, and not stored.
* Added <img> tags which will fetch 350 size the Arnold Clark images if the
  obfuscated value is valid.
* Use ng-change in the <input> fields to attempt obfuscation whenever the
  the contents of the fields changes.
* TODO: fallback method(s) for when images cannot be downloaded/404/500 etc.
* TODO: Valid tests for obfuscate function in MainCtrl