Smudge Versions Save

With the imminent release of Golang 1.11 and it's optional support for modules, I decided to take the current version, which is being used successfully by a number of folks (thanks!), and go ahead and release it as v1.0.0.

Once I figure out how to create a Go module, I'll set that up for you!

• 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.

With this release this project can be considered to be essentially feature complete: all major functionality that its authors have envisioned are in place.