Update 'README.md'

README.md

@@ -1,3 +1,11 @@
 # Caddy
 
-web server with automatic HTTPS written in Go
+web server with automatic HTTPS written in Go
+
+## Develop
+
+```
+$ git clone "https://github.com/caddyserver/caddy.git"
+$ cd caddy/cmd/caddy/
+$ go build
+```