Prevents NPE when using null for restricted command users
Merge pull request #33 from bendem/patch

Prevents NPE when using null for restricted command users
Some work on Channel join status

* Added a flag in Channel to see if it is joined or not
* Added easy way to get currently joined Channels in Server
* Added easy way to part a channel, see Channel#part()
Add FailedToJoinServerEvent. Easy. Fix #34
Actually implement Channel#part, lel
Fix #16
Add #30
Add Server to FailedToJoinServerEvent
Update README to recommend latest dev build
Set finalName of Alix jar file to Alix.jar