code: function (spring) {
        if (!spring) { return; }
        var idx = springs.indexOf(spring);
        if (idx > -1) {
          springs.splice(idx, 1);
          return true;
        }
      }
docs: Removes spring from the system
  
  @param {Object} spring to remove. Spring is an object returned by addSpring
  
  @returns {Boolean} true if spring found and removed. falsy otherwise;