in the majority of applications it makes sense to leverage as much horizontal space as possible to display attribution, primarily because of small form factor devices, but 55px is a little safer default because it accomodates a bottom oriented zoom control automatically.

since other possibly bottom aligned controls like L.Control.Scale and L.Controls.Layers don't have a static predictable width our best bet is to just expose a mechanism to let developers indicate just how much space should be reserved.

…ibution-width