Fragments: allow fragmentPrefix to define the entire delimiter

Bear with my pseudo-code for the sake of example. fragmentPrefix currently behaves something like this

var _rootPrefix = '#';
var _actualPrefix = _rootPrefix;

function fragmentPrefix( value ){
  _actualPrefix = _rootPrefix + value;

  var parts = this.toString().split( _actualPrefix );
  var uriProper = parts[ 0 ];
  var fragment = parts[ 1 ];
}

The way I'd like to see this work is to eliminate what I've called _rootPrefix above and just delimit with the supplied value. This would allow my current use case of working with Mithril, whose default SPA routing mode is to split on the search ?.

Start by locating the fragmentPrefix implementation and compare its current delimiter handling with the pseudo-code in the issue. Verify that a supplied value such as ? can act as the complete delimiter, including the Mithril routing use case, and confirm the existing fragment behavior remains covered.