* Show the connection duration upon departure
* humantime: ugly sub-second precision replaces grammatically incorrect "1 seconds" message
* simplify function name
* humantime: repair unit test
* move: util/humantime -> internal/humantime
* go fmt everything
#154
* Add `/ignore`/`/unignore` commands
* Move set to common package, use set for ignores
* `chat/set.go` is now `common/set.go`
* use `*IdSet` as type for ignored list for users
* remove `IsIgnoring` and `IgnoredNames` user functions, so to use directly `IdSet` methods
* refactor code accordingly
- Renamed chat.Channel -> chat.Room
- /ban works, supports IP also
- /whois works
- chat.User now accepts an Identifier interface rather than name
- Tweaked rate limiting