unicorn 0.97.0 - polishing and cleaning up

unicorn 0.97.0 - polishing and cleaning up

A bunch of small fixes related to startup/configuration and hot
reload issues with HUP:

* Variables in the user-generated config.ru files no longer
  risk clobbering variables used in laucher scripts.

* signal handlers are initialized before the pid file is
  dropped, so over-eager firing of init scripts won't
  mysteriously nuke a process.

* SIGHUP will return app to original state if an updated
  config.ru fails to load due to {Syntax,Load}Error.

* unicorn_rails should be Rails 3 compatible out-of-the-box
  ('unicorn' works as always, and is recommended for Rails 3)

* unicorn_rails is finally "working_directory"-aware when
  generating default temporary paths and pid file

* config.ru encoding is the application's default in 1.9,
  not forced to binary like many parts of Unicorn.

* configurator learned to handle the "user" directive outside
  of after_fork hook (which will always remain supported).

There are also various internal cleanups and possible speedups.