Fix rails_env option in schedules

As ENV['RAILS_ENV'] has been deprecated in Rails 3
and remove in Rails 3.1. I have left ENV['RAILS_ENV'] for backward
compatibility
Merge branch '116-fix_rails_env_option' of https://github.com/tech-angels/resque-scheduler into tech-angels-116-fix_rails_env_option

Conflicts:
	test/redis-test.conf
Touching up the env-based config loading bits

to use `Resque::Scheduler.env` instead of `ENV` and allow for both `env`
and `rails_env` config keys... because I shake my fist at thee, Rails!
Merge pull request #297 from meatballhat/env-config-load-touchup

Env config load touchup