Outline of elk from postgres example
There is nothing here that uses the config file path.
Add `remote_snapshots` to the interface and the in-memory implementation (`IFilesystem`).
More useful in-memory implementation of `IFilesystem.snapshots`.
Add a helper to check for the existence of the filesystem.  Use that to handle the no-snapshots case.
Do incremental pushes.

Change push to first retrieve the snapshots that exist remotely.
Supply this information to the local filesystem reader so it can construct an incremental stream.
Update the filesystem writer so it is capable of receiving incremental streams into the filesystem.
Push has become asynchronous - so propagate Deferred-handling code up the stack from it.
merge master
Debug gunk
Merge remote-tracking branch 'origin/master' into integrate-incremental-push-46
Merge remote-tracking branch 'origin/master' into elk-tutorial-563
Start with the flocker config proposed by Tom in https://github.com/ClusterHQ/docker-images/pull/7
add some pull commands
revert the change of node
Add a second deployment config with elasticsearch moved
Describe the components
More introduction
A note about the environment
Pull all three images on both nodes.
the first flocker-deploy step
log some messages