Finish partially implemented don't stop on error feature

[Cobular]

This is handled in the run_test function in the DiscordBot class, but the stop_error bool is never implemented by any tests. See below for it's current implementation, it basically suppresses the error.

https://github.com/JakeCover/distest/blob/c1d8de0be5ccb972775e4e5e0c125798bfc75f71/distest/bot.py#L41-L44

I haven't thought this through much yet, but it seems like all we need to do is:

• Implememnt this on a per-test basis (probably cascade some sort of continue-past-error varriable all the way to when a test is run)
• Write an example
• Document the feature

Notes: brought up when documenting for #21, possible 1.1 item