Disable Nagle's algorithm for beanstalkd connections

To test this:

a single worker that reserves a job and deletes it.
without this we get 25 jobs per second.

With this we get 1700 per second.

Inspiration: 
https://github.com/pascalopitz/nodestalker/blob/master/lib/beanstalk_client.js#L188
Merge pull request #20 from jtsoi/patch-1

Disable Nagle's algorithm for beanstalkd connections