Fix signin form width bug
Fix signin form width bug

No issue. Fixes bug where signin form was not expanding to its full width as a result of some earlier global changes. This sets an explicit fluid width with a max-width fallback so that it's always the correct size.

JohnONolan/Ghost-Admin,acburdine/Ghost-Admin,airycanon/Ghost-Admin,acburdine/Ghost-Admin,JohnONolan/Ghost-Admin,airycanon/Ghost-Admin,dbalders/Ghost-Admin,TryGhost/Ghost-Admin,TryGhost/Ghost-Admin,kevinansfield/Ghost-Admin,dbalders/Ghost-Admin,kevinansfield/Ghost-Admin