Use a real IRC object in some tests.

Additional functional tests of window.irc.IRC will need a full
object embedded in these tests, so make use of a real one rather
than an anonymous skeleton object.

While here, do some major CoffeeScript cruft cleanup.

[This is a commit prelude to a fixup of channel handling that will address #151 -- some code uses case-sensitive channel name comparisons, but the channels in the IRC.channels object are all lower case.]