Fixes issue with MutationObserver support in Poltergeist

Have removed the MO shim from the repo and it is instead included as
part of the mas-cms-editor Bower package. mas-cms-editor bumped to
incorporate latest changes.
Merge pull request #52 from moneyadviceservice/fix-poltergeist-js-issues

Fixes issue with MutationObserver support in Poltergeist
Merge pull request #51 from moneyadviceservice/tagging

Refactor is_taggable comfy extension
add page_name element to edit_page and set right css class to tags_chosen element
the rubocop code review merged externally removed some valid code.
test suite to page-tags associations