Any particular reason pgdriver doesn't support transaction isolation levels?

[iamgoroot]

Came across this piece of code

	if sql.IsolationLevel(opts.Isolation) != sql.LevelDefault {
		return nil, errors.New("pgdriver: custom IsolationLevel is not supported")
	}

Implementation seems pretty straightforward. I'm I missing something? Should I add support for this?

[vmihailenco]

I believe this was just not implemented in the first version and none ever asked for it so none bothered.

Should I add support for this?

Yes, please.

[iamgoroot]

Already merged into master