First challenge in the series - pretty straightforward but gets us familiar with how Maelstrom works. Basically just built a service that bounces back messages, but it's a good foundation for the more interesting distributed stuff coming up.
Takes in messages through STDIN
Sends them back with an echo_ok type
Keeps track of message IDs so replies match up with requests
Uses Maelstrom's Go library to handle the boring parts
Even though it's just echo-ing messages back, we're already dealing with:
JSON message passing between nodes
Proper request/response cycles
Message correlation (keeping track of which response goes with which request)
