Update: Use CommandModule

[sjrct]

We should use the command module for all modules that parse commands.

Relevant PR: halibot/halibot#36

[richteer]

Non-authoritative list ofcandidate modules for CommandModule. Not all are necessarily good fits for conversion, but it is worth taking a look at the following:

• dice
• mastermind (probably not)
• quote
• stackmemory
• tz
• emote
• timer (maybe?)
• btc
• reminders
• geoip
  probably others...

Some tips:

• look for modules that basically only ever react to a command
• modules that already split command logic into functions should be trivial to convert
• modules that have a lot of extra processing in .receive() may be a pain to convert
  • especially modules that also read bare strings or other sequences, unless you want to override .receive() carefully.