[tests] stabilize integration tests

Create integration test runner that supports before_suite and after_suite.
Use before_suite to configure ccm cluster size
Use @@ccm_cluster.setup_schema instead of creating new clusters with Cassandra.connect
Merge pull request #19 from datastax/integration-test-fix

[tests] use ensure to close cluster instances in tests
[RUBY-35] make sure host tokens are not nil
[CASSANDRA-7825] skip ghost nodes in system.peers table
[ci skip] update CHANGELOG
[ci skip] bump to the next development version
[ci skip] update current version in README
[ci skip] update Gemfile.lock
Fix broken Cassandra::Future.all
Merge pull request #21 from TalLevAmi/master

Fix broken Cassandra::Future.all