Convert restbase-cassandra into a new-style module
Convert restbase-cassandra into a new-style module

Remove the inline spec, and export operations only. This is intended to be
used with
https://github.com/gwicke/restbase/commit/fce27d997d4cfc46843b0b321dd2916bc8c0625b.

eevans/restbase-mod-table-cassandra,gwicke/restbase-mod-table-cassandra