Split single binary into separate stats-sink and api-server binaries

[mredivo]

For robustness, it's probably a good idea to make separate binaries for the separate functions performed by Cassabon:

• Receive stats and write them to storage
• Serve HTTP requests for stats paths and stats

With this change, if the HTTP server dies, it doesn't take down a stats writer with it.

This shouldn't involve much new code, all the functionality is already present.

[jeffpierce]

I'm okay with this.

[jeffpierce]

Actually...does it make more sense to just have flags that allow Cassabon to run in carbon only or API only mode rather than splitting the binary?

[utkarshcmu]

Same binary with flag is a better way, IMO. The reason being, no hassle in deployment different binaries.

[mredivo]

That's a valid point. A command-line argument to control what it does, and all other functionality is bypassed.

Might also be an idea for the new bootstrap functionality.