Update README.md

Hi Stuart - I was trying out your cool component framework and noticed an inconsistency between Database and ExampleComponent.  I thought the above change would clarify the docs for your readers.  Do you agree?
Alan
looking again, I find the example to be a bit unintuitive. The connection is passed in to the record, but it's not used anywhere in the record and `start` creates a `conn` using the `host` and the `port` parameters, so you would assume that the `conn` associated with the `:connection` key would be the actual connection. Also, why pass the connection to the component instead of initializing it in the `start` function, which seems to also be happening.