Bump version number to 1.0.18 (#307)
Bump version number to 1.0.18 (#307)

As 1.0.17 is released, the version should be bumped to 1.0.18.
szhou1234/dcos-cassandra-service,mesosphere/dcos-cassandra-service,mesosphere/dcos-cassandra-service,arun24816/dcos-cassandra-service,arun24816/dcos-cassandra-service,niteshjain1/dcos-cassandra-service,mesosphere/dcos-cassandra-service,niteshjain1/dcos-cassandra-service,szhou1234/dcos-cassandra-service,akshitjain/dcos-cassandra-service,akshitjain/dcos-cassandra-service,akshitjain/dcos-cassandra-service,Pranav02/dcos-cassandra-service,niteshjain1/dcos-cassandra-service,szhou1234/dcos-cassandra-service,Pranav02/dcos-cassandra-service,adobe-mds/dcos-cassandra-service,akshitjain/dcos-cassandra-service,akshitjain/dcos-cassandra-service,szhou1234/dcos-cassandra-service,szhou1234/dcos-cassandra-service,niteshjain1/dcos-cassandra-service,arun24816/dcos-cassandra-service,arun24816/dcos-cassandra-service,mesosphere/dcos-cassandra-service,Pranav02/dcos-cassandra-service,mesosphere/dcos-cassandra-service,adobe-mds/dcos-cassandra-service,arun24816/dcos-cassandra-service,niteshjain1/dcos-cassandra-service,Pranav02/dcos-cassandra-service,Pranav02/dcos-cassandra-service,adobe-mds/dcos-cassandra-service,adobe-mds/dcos-cassandra-service,adobe-mds/dcos-cassandra-service