Allow API key authentication.

[BarthV]

https://github.com/lightspeedretail/ruby-grafana-api/blob/master/lib/grafana/client.rb#L68
⬇️
Currently Client.new only accept user / pass auth.

We should be able to log with an API key.

Thanks for your time & your work ;) !

[BarthV]

PR submitted :)

[nicolasbrechet]

Hello,

I would love to see this merged, any chance it can be done ? 😃

Thanks !

[BarthV]

@hartfordfive ? ^