Fixing the HAML bug

We used to have a very annoying problem in our sites.

Every time we deployed - no wait - every time we *imported* fixtures, whatever the environment was, some links suddenly changed from e.g. `/foo` to `<!-- foo -->`.

After some investigation we found out that the problem was a `read_as_haml` method from Comfy.

We're sure it wasn't supposed to be a problem, but a feature. Chances are the maintainer of Comfy was thinking of the `rake cms:fixtures:import` as a one-off task: deploy, import fixtures, *done*. 

It may be useful indeed to take advantage of a HAML parser in this case, *but* actually this feature caused us the problem stated above ([Trello card](https://trello.com/c/BvNJGNR7/1414-users-shouldn-t-be-able-to-execute-arbitrary-haml-from-cms-admin-aka-broken-links)).

With this PR we are managing to remove this feature/bug from the platform.

@homeserve-alliance/dev-team