code: function( rules ){
  
              var self = this
                  ,fn = (typeof rules === 'function') ? rules : Physics.query( rules )
                  ;
  
              return Physics.util.filter( self._bodies, fn );
          }
docs: see: Physics.query
  Physics.world#find( rules ) -> Array
  Physics.world#find( filter(body) ) -> Array
  - rules (Object): Query rules
  - filter (Function): Filter function called to check bodies
  - body (Body): Each body in the world
  
  Find all matching bodies based on query rules.