Features added

• Bug fixed in parsing environment variables.
• Fixed a bug that caused a panic when nonexistent hosts were added.
• Status update messages are now tagged with the heartbeat number of the node in question; if the most recent known status of a node is newer than the tag, the message is ignored.
• If a node doesn't have any new updates to emit, it instead emits the current statuses of up to sigma * log(N) known nodes.