first stab at Ruby bindings

This will need some serious optimization in the future, but it's a good
start to a high-level interface to the debci data store
drop usage of faketime in test suite

faketime kept as build dependency for convenience for developers
Finish Ruby API for now
backends/fake: output a timestamp like the ones adt-run outputs
test: extract DEP8 helper to avoid duplication
debci-config: helper to output value of debci configuration values
debci-generate-feeds: generate a per-package feed
document the Ruby API
document relevant news in debian/changelog
avoid crashing with invalid JSON input
mark bug closes in this new version