Removes static optimizely script and adds a dynamic one.
Adds caching to optimizely tag helper.
Merge pull request #394 from moneyadviceservice/f/optimizely

Adds dynamic optimizely script.
Skeleton Breadcrumbs reader
Rename CategoryNavigationReader for wider usage
Mind blowing breadcrumb reader
Return categories as a tree structure
Add breadcrumbs reader
Use category tree
Replace primary_navigation_spec by category_navigation_decorator_spec
Use VCR for HTML validation features
Use fixtures for article acceptance tests
Add acceptance tests for article breadcrumbs
Add acceptance test for category breadcrumbs