Fixing deprecation warnings
Allow for multiple hooks in after_prefork

Existing versions of Resque::Pool will only allow one caller to set the
`after_prefork` hook. When this is used for something like reestablishing the
ActiveRecord connection, it prevents other libraries from safely registering
their own hook.
Remember to reset the RESQUE_POOL_CONFIG environment variable
Change process group for workers (by default)

Turn off with `export RESQUE_SINGLE_PGRP=YES` or `--single_process_group` flag.
Merge pull request #83 from mattdbridges/fix-order-dependent-specs

Fix order dependent specs
Merge pull request #81 from darbyfrey/master

Fixing deprecation warnings
Merge branch 'multiple_after_prefork_hooks' of https://github.com/jasonrclark/resque-pool into jasonrclark-multiple_after_prefork_hooks
preserve Principle of Least Surprise after_prefork= but also keep new multi-hook after_prefork behavior.