Implement keep file for #6

Closes #6 by implementing a keep/exclusions file.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

add compression to binaries

Signed-off-by: Richard Gee <richard@technologee.co.uk>

Don't remove if there are zero or no reachable contexts

When run on start-up, if there is no WiFi available, we want to
preserve the clusters, or allow the user to --force the removal.

When there are zero changes to make, don't write out the file.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

Add .DEREK.yml file for release notes

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

Add README

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>