Add usage example to README

[pirate]

This looks very cool! I'm just curious how to use the CLI interface and Web interface. (and is the web UI required / or is the CLI the main interaction method?)

First I tried passing the ping target using --peers with a hostname

Host 1: macOS Catalina (Go 1.15)

git clone https://github.com/benjojo/sping && sping
go build
./sping --peers lemon.local
2021/03/02 23:26:37 Listening on[::]:9523

# no stats are printed to CLI or visible in web UI on http://127.0.0.1:9523

Host 2: Ubuntu 20.04 (Go 1.13

git clone https://github.com/benjojo/sping && sping
go build
./sping --peers lime.local
2021/03/02 23:26:40 Listening on[::]:9523

# but no stats are printed to CLI or visible in web UI on http://127.0.0.1:9523

Then I tried using IPs instead of hostnames with no luck

Host 1

# on Host 1
./sping --peers 192.168.1.177
2021/03/02 23:30:33 Listening on[::]:9523
2021/03/02 23:30:33 Cannot (TCP) handshake to 192.168.1.177: dial tcp 192.168.1.177:6924: connect: connection refused
2021/03/02 23:30:34 Cannot (TCP) handshake to 192.168.1.177: dial tcp 192.168.1.177:6924: connect: connection refused
...

Host 2

# on Host 2
./sping --peers 192.168.1.41
2021/03/02 23:32:22 Listening on[::]:9523
2021/03/02 23:32:22 Cannot (TCP) handshake to 192.168.1.41: dial tcp 192.168.1.41:6924: connect: connection refused
2021/03/02 23:32:23 Cannot (TCP) handshake to 192.168.1.41: dial tcp 192.168.1.41:6924: connect: connection refused
...

Question

How can I get the node1->node2 = ??ms and node2->node1 = ??ms latency average between two hosts using the ./sping CLI or Web UI?