Use http://www.mysociety.org instead of its robots.txt in a test
Use http://www.mysociety.org instead of its robots.txt in a test

Since the site redesign there has been no
robots.txt file for mysociety.org, but one of the hansard
tests assumed it would be present, as an arbitrary file
to fetch and test caching of.  Any web page will do, so
just use http://www.mysociety.org

Fixes #680

mysociety/pombola,patricmutwiri/pombola,hzj123/56th,ken-muturi/pombola,ken-muturi/pombola,patricmutwiri/pombola,ken-muturi/pombola,patricmutwiri/pombola,geoffkilpin/pombola,patricmutwiri/pombola,geoffkilpin/pombola,patricmutwiri/pombola,mysociety/pombola,geoffkilpin/pombola,mysociety/pombola,ken-muturi/pombola,hzj123/56th,mysociety/pombola,geoffkilpin/pombola,mysociety/pombola,mysociety/pombola,hzj123/56th,geoffkilpin/pombola,hzj123/56th,hzj123/56th,ken-muturi/pombola,patricmutwiri/pombola,geoffkilpin/pombola,hzj123/56th,ken-muturi/pombola