Upgrade to the latest image-proxy package from npm
Upgrade to the latest image-proxy package from npm

Now that the latest master version of image-proxy--which contains the
fix for the 504 errors we were seeing--has been released to npm we can
just run that directly rather than using the git version.

mysociety/popit,mysociety/popit,Sinar/popit,mysociety/popit,openstate/popit,openstate/popit,Sinar/popit,Sinar/popit,openstate/popit,Sinar/popit,openstate/popit,mysociety/popit,mysociety/popit