Update & Write tests for all the commands

[frereit]

The code hasn't been touched in a while and is probably outdated in some places (API changes, etc.). While we're at it, we should also consider writing a second discord bot that just tests the first one. This has the advantage that the tests are as close to the user experience as possible and bugs with the discord api will be caught early on. Of course conventional unit tests are also nice. Feel free to open seperate issues for each of these categories, just make sure to link back here and don't forget to mark this as completed!

• Discord API & Base Class
• Cryptorgraphy Module
• Cryptocurrency Module
• Help Module
• Math Moduel
• News Module
• Music Module
• Translate Module