Integrate log handlers into zmq io loop.

Currently, circus polls logging handlers once every second.  This is inefficient,
and easily stalls processes that emit more log messages in one second than fits
into the systems pipe buffer (typically 4-64 KB).  I have actually seen this
happening with BrightcoveOS's Diamond server.

This change integrates log handling into the zmq ioloop, which should handle any
amount of log traffic fairly and without arbitrary delay.
Make redirector restartable and subsequently more robust.
PEP8 fixes.
One more pep8 fix.
Update configuration.rst

worker ID is not WID anymore but circus.wid
I guess same is true for ENV.VAR (circus.env.var ?) But I cannot find it in the unittest :)
Merge pull request #392 from jul/patch-1

Update configuration.rst
Merge branch 'lambdafu/logio' of https://github.com/lambdafu/circus into lambdafu-lambdafu/logio
fix the redirection
Fix two failing tests on Mac OS X with python2.7.4
remove the zmq indirection
using the green loop if we detect gevent
Merge pull request #393 from Lothiraldan/master

Fix two failing tests on Mac OS X with python2.7.4
Added an example for #386
typo
more test coverage
updated dependencies
added vim undos
Added support for CIRCUSCTL_ENDPOINT environment variable to circusctl
fixed typo - fixes #395
util: fix bug in to_uid function

It must check for string_types, not str only.