Not doing so made it trickier to define a flex layout, since the
icon-successful element is given a `position: absolute`, but only for
successful proposals, while for unsuccessful proposals it was taking
the standard `position: static` value.
We're also reusing the `successful?` method instead of rewriting it in
the view, and fixing a small issue where the icon wasn't displayed for
proposals having the exact needed votes (we were using `>` instead of
`>=` in the condition).
Note that legislation proposals use the method
`Proposal.votes_needed_for_success`, which is probaby a mistake caused
by copying the code from the proposal view. Fixing this issue is out of
the scope of this commit (and pull request), though.
1ae4caa0ef