implements retry after timeout @ req send method

Trying to figure out how to have a "retry after timeout" on zeromq i end up in this thread:
https://github.com/JustinTulloss/zeromq.node/issues/211

As said RCVTIMEO and SNDTIMEO are not supported, so then i came out with this "simple approach".

Not sure if you would like to merge into the project, anyway here is how i solved on my side.

peace
:v: