Blackhole logging system has been injected into cocaine.
Merge pull request #89 from 3Hren/ft-Logging

New logging system.
Raft leader becomes follower if it can't communicate with a quorum.

If a leader can't communicate with a quorum, it can't process requests, but accepts them to the log. It may lead to filling the log with requests, which will not be processed in a reasonable time. So it's better for a leader to become follower and discard requests.
Fixed removing of nodes from cluster.

Before removing of node was supposed to be manual procedure. An administrator was supposed to remove the node from configuration mashine via control service and then shut down the node to disable its activity. Now a node always automatically stops any activity during removing of it. So nodes may be safely removed by any program.
Fixed automatic disabling of removed Raft leader.

When a leader removes itself from the cluster, it continues to be a leader, but doesn't count own votes during elections and replication. It's totaly safe but may be confusing. So now leader disables itself, after it commits self removing from the cluster.