Add general voting using the instant-runoff system

electionbot: add general vote with ranked voting

* Based on the instant-runoff system.

* Also, I added a "lite" registration for users who weren't registered.
  Everyone can do this final vote.

Move from FPTP to Runoff

electionbot: convert from a FPTP to Runoff voting system

* To do this, I added a rnominate command for the second stage.

* I split off many common operations into their own functions

* I also expanded the help message after neglecting it.

Add 'dropout' command

electionbot: add dropout command

* This command allows a user during stage 2 to dropout of the campaign,
  and transfer all of their votes to another user. They then can never
  be voted for again, and cannot have someone transfer their votes to them.

Fix mention parsing

electionbot: fix bug where some mentions don't get parsed

* When a user has a nickname, their mention starts with '<!@'
  Otherwise, it starts with '<@'.
  I only accounted for the nickname case. Now, the code checks
  for both, then removes it accordingly

Stage enforcement

electionbot: add stage enforcement

* Since not every option should be available at once,
  I added staging to gate each command.

Initial release

electionbot: add nomination function

* There is now a command that will allow a user to select one nominee from their party

* I rewrote the register command to be significantly less expensive.

* Added a command to get the top 5 nominees for each party