Does not support EventStore 4

[BookOfGreg]

I realise this gem supports EventStore 3, there's the potential for me to contribute to support EventStore 4.

Using this gem I can insert events into ES4 just fine, but cannot read them back as it always returns [] from any method in actions such as https://github.com/arkency/http_event_store/blob/master/lib/http_event_store/actions/read_all_stream_events_forward.rb

I've followed execution as far as https://github.com/arkency/http_event_store/blob/master/lib/http_event_store/actions/read_all_stream_events.rb#L11 and it looks like the issue may be with the parser, the assumption being format of events coming back in ES4 is different.