Update config file everytime "history" message received

[canklot]

So that we can make changes on config file like on Channel id and path to save and dont have to restart the bot to apply changes

[get-got]

That is a feature in my fork ( https://github.com/get-got/discord-downloader-go ) but maybe next time I mess with this one and make a pull request I'll add that.

In the fork it will reload your settings every time it detects the settings file was modified, should always be instant.