Tests and interactive messages #126

Create tests for Duga's more interactive abilities, and also add more/better support for it.

For example, test the following:

• Duga signup
• Duga gives a link with instructions
• Duga (some one-time key provided by Duga)
• Duga says: OK or something

Another one:

• Duga tasks
• Duga responds with current task information

Another one:

• Duga add task XYZ ABC
• Duga adds a new task

Another one:

• Duga issue 42
• Duga informs about issue 42