hz 3.9 support needs

[donovankim]

error occured on hz 3.9 like below
com.noctarius.snowcast.SnowcastException: Found an unknown Hazelcast version

[noctarius]

Hey @donovankim,
right now there's no official support for Hazelcast 3.9, however @lukasherman is working on it.
Unfortunately I don't have time right now but whenever finished I'm happy to merge and to release.

#19

[lukasherman]

PR now looks good to me. Version bump to 2.1.0-SNAPSHOT, removed backward compatibility, code cleanup.