unicorn 0.991.0 - startup improvements

The "working_directory" configuration parameter is now handled
before config.ru.  That means "unicorn" and "unicorn_rails" no
longer barfs when initially started outside of the configured
"working_directory" where a config.ru is required.  A huge
thanks to Pierre Baillet for catching this ugly UI inconsistency
before the big 1.0 release

Thanks to Hongli Lai, out-of-the-box Rails 3 (beta) support
should be improved for deployments lacking a config.ru

There are more new integration tests, cleanups and some
documentation improvements.