Make a new urllib package .

It consists of code from urllib, urllib2, urlparse, and robotparser.
The old modules have all been removed.  The new package has five
submodules: urllib.parse, urllib.request, urllib.response,
urllib.error, and urllib.robotparser.  The urllib.request.urlopen()
function uses the url opener from urllib2.

Note that the unittests have not been renamed for the
beta, but they will be renamed in the future.

Joint work with Senthil Kumaran.