pgGo v0.1.1

Adds a runnable example, so you can try pgGo without installing anything:

DATABASE_URL=postgres://user:pass@localhost:5432/db \
  go run github.com/pgrundev/pggo/examples/hello@latest

It prints the server version, the result of SELECT 1, and the elapsed time. The library and CLI are unchanged from v0.1.0, and the README now shows install instructions and a usage example at the top.