Fix trailing slashes output app-wide
Fix trailing slashes output app-wide

closes #2963, closes #2964
- override Ember's `HistoryLocation.formatURL`
- remove overridden `HistoryLocation.setURL`

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