code: function (key) {
                  var r = []
                  this.all(function(a) {    
                      for (var i = 0, l = a.length; i < l; i++) {
                          if (a[i] != key) r.push(a[i])
                      } 
  
                      var _set = {}
                      _set[this.key] = JSON.stringify(r) 
                      storage.set(_set)
                  })
              }
docs: deletes a key from the index