Set up Tweepy authentication using passed args or config file settings.

def setup_auth(**keys):
    '''Set up Tweepy authentication using passed args or config file settings.'''
    auth = tweepy.OAuthHandler(consumer_key=keys['consumer_key'], consumer_secret=keys['consumer_secret'])
    auth.set_access_token(
        key=keys.get('token', keys.get('key', keys.get('oauth_token'))),
        secret=keys.get('secret', keys.get('oauth_secret'))
    )
    return auth