add Slack group to the readme
add Slack group to the readme
bitjson/hivemind,bitcoin-hivemind/hivemind,bitcoin-hivemind/hivemind,bitjson/hivemind,bitcoin-hivemind/hivemind,bitjson/hivemind,bitjson/hivemind,bitcoin-hivemind/hivemind,bitjson/hivemind,bitcoin-hivemind/hivemind,bitcoin-hivemind/hivemind,bitjson/hivemind,bitjson/hivemind,bitcoin-hivemind/hivemind