Res stream example

this build off the previous PR https://github.com/request/request/pull/1269

> merging in order should be fine, i made this difficult didn't i? ... sigh, time for the weekend :boom:

* adds additional example for handling "response" events, copied from https://github.com/request/request/issues/1268
not sure what value this code block adds, it seems very confusing, especially to a newbie. Could you distill this down to a single, smaller concept?