Common test

And of course, I managed to include the IRCConnection tests in here -.-
Basically contains some stuff common between tests, some fixes for some tests, and some misc. fixes.

Some important stuff from one of the commits;
```
Corrected quit function
See http://www.irchelp.org/irchelp/rfc/chapter4.html#c4_1_6 for reasoning.
In short, if no message is provided for quit, the default should be the
nickname.
```