Moved semi-static command line arguments to settings.
Fixes #3 by limiting the number of simultaneous requests.

Other settings CONCURRENT_REQUESTS_PER_DOMAIN and CONCURRENT_REQUESTS_PER_IP
were also checked but neither fixed the error.

Since the spider only handles the checklists for one region, restricting the
number of concurrent requests to 1 should not adversely affect performance.
Bumped version number to 0.1a2
Merge branch 'release-0.1a2'