Unit tests fail if nicks.csv does not exist

[zxiiro]

Before a contributor can run unit tests it is assumed that the user has a created a nicks.csv file in their WelcomeBot directory. Proper unit tests should create required files in the setUp() function and remove them during tearDown().

Traceback (most recent call last):
  File "test_bot.py", line 41, in setUp
    self.bot = botcode.Bot()
  File "bot.py", line 25, in __init__
    with open(self.nick_source, 'rb') as csv_file:
IOError: [Errno 2] No such file or directory: 'nicks.csv'