Argument parser added!

-s, --sites: specify a list of sites (otherwise defaults to Alexa)
-g, --generate: Use the Alexa (or specified list) and write out working
sites to a different file.
-n, --no-results: don't write results to file (to be implemented)
-m, --max-site: set the max number of sites to test. Default is 20.

TODO
-- Add result recording