TestMiscProtocolRedirect doesn't support fragments

Document the fact that none of our vendors preserve URL fragments when
redirecting from HTTP to HTTPS. The same is also true of the bare redirect
that we're about to setup - noticed by Matt. I'm indifferent about whether
this is the *correct* behaviour.
Merge pull request #99 from alphagov/redirects_dont_support_fragments

TestMiscProtocolRedirect doesn't support fragments