* Throw when attempting to add or remove a member's EveryoneRole

This resolves #780

* Removed braces

This resolves #784

* Add support for audit log reasons

* Made changes per discussion

Messages may only be pruned between 0 and 7 days, otherwise a 400 will be thrown.

* Removed GuildUserExtensions and moved the methods to IGuildUser and implementations

* Made changes per fox's suggestion: Change->Modify. New Modify overload.

* Oops

* Per Volt: reimplemented new endpoints

* Fixing broken docstrings

* I forgot that docstrings are XML

* Implemented atomic add/remove role endpoints

* Removed  so people aren't irked

* Added single-item role add/remove methods

This resolves #477