Better README and starter guide

[thinkingfish]

We should add a "Getting Started" guide and update README.md, on common issues such as what binary to use for what purpose, how to config server, and how to verify that the configuration works as intended by issuing simple commands and verifying server status.

This will be a good start to bootstrap the effort to write much better and much more documentation, which should be integrated into pelikan.io

[thinkingfish]

cc @chenfeining