Merge pull request #748 from simong/pp-links

PP - Check if a http link is available on https (and vice versa)
(Issue 815) Fix event listener leak in PP tests
Merge pull request #815 from mrvisser/issue-815

Event Listener leak in unit tests
Fixing Express to version 3.4.8

Express has opted to publish their release candidates to npm. Since we
were binding to `latest` and quite a few things changed in 4.0.0 there
will be a bit of work required to migrate to 4.0.0.

Reverting to 3.4.8 in the mean time