Add --error-trace to lucky watch / lucky dev

[jwoertink]

When running your app through lucky dev, there's no way to pass --error-trace currently. We need a way to proxy that down to this command.

We could have lucky dev --error-trace or maybe you just edit your Procfile.dev (which would probably need to happen anyway), and update lucky watch --error-trace.

[carcinocron]

any way to see stack traces before this is merged?

[jwoertink]

@InstanceOfMichael You can just boot your app with crystal src/start_server.cr --error-trace. You just don't get the nice compile watcher, but if you make a change, just kill the server and start back up manually.