Allow customization of the "request" module used by client API

[rfk]

I'd like to use the Client API code for writing a loadtest suite. To make this work well, I would need it to use a customized "request" module object that can monitor and report on each outgoing HTTP request.

I made a first pass at this in the following commit, but it's pretty inelegant:

007a390

You can see how I intend to use such functionality here:

4c1fca7#L2R14

@dannycoates @zaach thoughts on the best way to achieve such functionality?

[dannycoates]

@rfk I don't see anything wrong with your approach, however an alternative would be to make ClientApi an EventEmitter. I've used that approach for diagnostics before, in poolee for instance.

Then you could do something like:

client.api.on('stat', function (stat) { runner.send('add_hit', stat) })

Off topic but I think the client module deserves some refactoring in general soon, once we get a feel for its usage.

[rfk]

EventEmitter +1, that sounds a lot cleaner from an API standpoint. I'll continue with my hacked up version for now, and we can consider a more holistic refactoring sometime soon.