Updated Brakeman

Updated the gem and the ignore file with the new
function definitions
Enabled 'protect_from_forgery'

Don't know why it was commented out.
The comment doesn't explain it.
Enabled brakeman
Merge pull request #224 from ministryofjustice/brakeman-update

Brakeman update. Note that 'protect_from_forgery' may break submission of form after a deploy by users who are filling form during a deploy.