Make the organisation dropdown a decent size for the values within it
Make the organisation dropdown a decent size for the values within it

- Fixes #169 after just over a year!
- This now stays at a decent size with and without JavaScript on. I
  chose `input-md-5` out of thin air, but most of the org titles now
  display fine in the dropdown, and it's better than it was!

alphagov/contacts-admin,alphagov/contacts-admin,alphagov/contacts-admin