waiting for schema agreement after delete query
Merge pull request #75 from dukhlov/master

waiting for schema agreement after delete query
Cassandra backend: 'exclusive_start_key' full version
Cassandra backend: paging for 'scan'
Cassandra backend: support for extra conditions for 'scan'
API: 'Scan' support
Merge pull request #76 from ikhudoshyn/api-scan

Api scan