Some streams will occaisonally advance their positions without actually
having any new rows to send over federation. Currently this means that
the token will not advance on the workers, leading to them repeatedly
sending a slightly out of date token. This in turns requires the master
to hit the DB to check if there are any new rows, rather than hitting
the no op logic where we check if the given token matches the current
token.

This commit changes the API to always return an entry if the position
for a stream has changed, allowing workers to advance their tokens
correctly.

Signed-off-by: Stanislav Nikitin <pztrn@pztrn.name>

Added boilerplate for running end-to-end tests.\nThis is done using Protractor, which looks for a .gitignored file environment-protractor.js which contains the selenium endpoint url.

WIP: Completely change how event streaming and pagination work. This reflects the change in the underlying storage model.