Convert icecast2.py to use Requests library instead of pycurl and urllib2

I've also made the icecast2.Admin() constructor/init less complicated. No reason to pass the icecast admin values like that.

    - self.icecast_admin = icecast2.Admin(
    - settings.ICECAST_HOST + ":" +
    - str(settings.ICECAST_PORT),
    - settings.ICECAST_USERNAME,
    - settings.ICECAST_PASSWORD)
    + self.icecast_admin = icecast2.Admin()