pipeline: lock at known-good trollius revision.

Trollius 1.0.1 contains a bug that, over time, causes wpull to fail to
retrieve data over any connection.  The unreleased Trollius 1.0.2 will
contain a fix for this, but -- well -- it's unreleased.  Stopgap
solution: use their Mercurial repo.
Make the test server exhibit more interesting behavior.

Specifically, this commit adds multiple links on each test page.  This
means that concurrency levels > 1 will actually engage multiple workers.