set ForwardedAllowIPS via cli
Run worker's setup early than set num_workers

`cfg.worker_class` is a property, which calls the classmethod `setup` of
the worker class when accessed.  Gevent worker relies on this mechanism
to call `gevent.monkey.patch_all()`.

However, `num_workers` is a hooked property, when it is set, gunicorn
will call hook defined by user.  If the hooked code relies on
gevent's monkey patch, it will fail because the monkey patch has not
been applied yet.

This commit makes sure that `worker_class` property getter invokes
before `num_workers` setter to resolve this problem.
Split access_log_format specifiers description into multiply lines
Correct sphinx-build error: source/settings.rst:762: ERROR: Inconsistent literal block quoting.
proxy_allow_ips: Allow proxy protocol if "*" specified.

This makes proxy_allow_ips symmetrical with forwarded_allow_ips and is
useful in the same situations.
don't depend on entry point for internal classes.

We don't have to depend on entry points when loading suppoorted workers
nad extensions, instead use the absolute path to load the class.

fix #259
use import_module instead of our own hack to import the module
Merge pull request #667 from spladug/proxy-protocol-allow-star

proxy_allow_ips: Allow proxy protocol if "*" specified.
add worker_int callback

fix #516
fix tests under py3
Merge pull request #666 from ipetrov/correct_docs

Small changes at docs
ease the doc. test with the default rtd theme
fix doc for rtd
Make WorkerTmp accept a configurable tmp dir
Merge pull request #649 from hongqn/gevent-patch-early

Run worker's setup earlier than set num_workers
fix typo
Merge pull request #642 from georgexsh/forward_ips_cli

set ForwardedAllowIPS via cli
add missing cli = --x-forwarded-for-hdr option
fix sendfile with SSL
Added support for more options to ssl.wrap_socket