Replace deprecated gist API in help

[hekel]

Resolves #1254

[dgw]

Just as a general comment, replacing gists with another service that supports HTTPS would be ideal. Something like https://ptpb.pw/ perhaps?

[kwaaak]

I like Hastebin (https://hastebin.com/about.md), a service with some ephemerality would be a good choice. Expiration in well under 24 hours should be more than enough.

[anarcat]

generally LGTM, although this could break again when/if ix.io fails in turn. shouldn't we find a better way to dump the command list? why not just dump the command list a line at a time like other bots? :)

[dgw]

@anarcat See #1080 for one reason why Sopel no longer simply dumps the command list en masse. That said, changing from Gist to another pastebin provider (ix.io is not final) is merely one part of the solution. Eventually the plan is to have a local HTML/text option that can be hosted from the server Sopel runs on, and perhaps also have an option to turn the "deluge of PMs" method back on if it's really wanted.

[anarcat]

hmm... yeah okay, that makes sense - thanks!

[dgw]

I like it (but I'll stop short of putting a ring on it, mostly because pythons don't have fingers).

[dgw]

@anarcat, want to take a second look before I merge this?

[anarcat]

LGTM.