code: function(eventName, callbackToRemove) {
        if (callbacks[eventName]) {
          for (var i = 0; i < callbacks[eventName].length; i++) {
            if (callbacks[eventName][i] === callbackToRemove) {
              callbacks[eventName].splice(i, 1);
              break
            }
          }
        }
      }
docs: @method off
  @memberof salep
  
  @desc
  This function allows removing callbacks from events. Every callback
  added with 'on' function can be removed with this function.
  
  @param {String}    eventName         Event name to remove callback from
  @param {Function}  callbackToRemove  Callback to remove
  
  @example
  function myCallback(test) {
  // do some stuff
  }
  salep.on('testStart', myCallback);
  ...
  salep.off('testStart', myCallback);