Ratelimits fixes and new models

Breaking changes

• Message mentions have been moved to Message.mentions as a Mentions object to provide more functionality

Features

• GuildMember.ban is now implemented
• Prebuilt documentation indexes for faster loading times
• New rest.search_members endpoint

Bug fixes

• Running expensive logging functions when logging was not enabled
  • This slowed down requests, which wont happen now.
• Implemented a lock on requests which only allows 1 simultaneous request to aid ratelimiting
  • Should help bots which use a lot 1 single endpoint, as there will be no more 429's

Package version bumps

• attrs (20.2.0 -> 20.3.0)
• colorlog (4.4.0 -> 4.6.2)
• multidict (5.0.0 -> 5.0.2)