Fix for intermittent push unit test failures

Bug: The activties were being delivered on the websocket before we had
bound the `message` event listener.

Fix: Bind the event listener in the same process tick as we perform the
action for which we should receive a message on the socket.

The tests have also been cleaned up a bit as they were performing
unnecessary activity collections (push notification happens on routing,
there’s no need for aggregation/collection)
Fix broken push tests
Merge pull request #897 from simong/intermittent-push-failure

Fix for intermittent push unit test failures
don't check coverage on external node_modules
Fix express to 4.2.0 due ot build break
fix variable names, cleaner filter
Merge pull request #906 from stuartf/coverageIgnoreExternal

don't check coverage on external node_modules
Merge pull request #907 from mrvisser/express-4.2.0

Fix express to 4.2.0 due to build break