Replaced bot messaging with irc.reply() for some methods.

- Replaced instances of irc.sendMessage() and irc.error() with irc.reply()
  in TriviaTime.stop(), TriviaTime.start(), TriviaTime.skip(),
  TriviaTime.repeat(), TriviaTime.next() and TriviaTime.time()
- Used the parameter 'prefixNick=False' in cases where the reply shouldn't
  include the caller's nick as a prefix