Exclude and include channels on Server Messages

[casperstorm]

This PR solves the following problems:

1. You want to see join in all channels except #linux and #halloy.
2. You dont want to see part in any channels except #linux and #halloy.

This is now solved by exclude and include

# 1. see join messages in all channels except #linux and #halloy.
[buffer.server_messages.join]
exclude = ["#linux", "#halloy"]

# 2. don't see part messages in any channels except #linux and #halloy.
# The "*" (or "all") is a wildcard which means all channels.
[buffer.server_messages.join]
exclude = ["*"]
include = ["#linux", "#halloy"]

If the channel is included, it has precedence over excluded and enabled is above both so the following wont show any message at all:

# dont see any quit messages in any channel
[buffer.server_messages.quit]
enabled = false
include = ["*"]

• Update CHANGELOG
• Update book