add `--threads` param
add fdevents module

This module add a new cross platform event poller to gunicorn. It allows
you to listen on different fds in an efficient manner.

On linux it's using epoll, bsd/darwin kqueue...
add missing gthreads worker
fix the fdevents module
fix ThreadWorker
fix keepalive
fix PollPoller
fix kqueue poller.

this change initialise the event loop after the process has forked so we
make sure to inherit from the file descriptor.

Also fix the number of events we are waiting for. The python
implementation requires a positive number.
compatibility with python 2

Add support of the threaded worker on python 2.7. python 2.7 has no
futures module. With this change the compatibility module is installed.
reuse the code
Fix a couple of typos.
Fix markup of the access_log_format documentation.
Merge pull request #755 from berkerpeksag/fix-typos

Fix a couple of typos.
Merge pull request #756 from berkerpeksag/fix-markup-log-format-doc

Fix markup of the access_log_format documentation.
Sync settings documentation with gunicorn/config.py.
Merge pull request #757 from berkerpeksag/update-settings-doc

Sync settings documentation with gunicorn/config.py.
Remove reference to unmaintained py24 branch
Update deploy.rst
Merge pull request #760 from TedWantsMore/patch-1

Update deploy.rst
Use six.string_types instead of basestring.