Nick change failure on freenode

Hi there!

First of all, thank you for this library. I have been needing something like it for nearly(over?) two years, and when I found this library I was overjoyed `:)`

Now on to business! I discovered that after changing my nick (on freenode), the value in my `bot.nick` is not what I expected. I discovered that the regex for `NEW_NICK` did not exactly match what I was getting from freenode. I hope this patch is acceptable.