Remove the currently_met field from Maslow

This question on the form is redundant as it is
confusing most of our users in testing, and the
users which actually require this information
already capture it through another process in the
transition project.

This should be merged before we remove this from
the Need API. Maslow can create and update needs
fine without this field as it gets set to null in
the API.
Merge pull request #35 from alphagov/remove-currently-met-question

Remove the currently_met field from Maslow