No need to require when loaded via Gemfile
Allow ScriptRedis class to override Redis instance used by runners; add NilRedis implementation for turning off Redis
typo fix for README
DRY out convenience method declarations on Scripterator module
Add configuration class and allow it to control Redis instance
Loosen ActiveRecord version requirement
Add config block instructions to README
Add config option for Redis expiration time
Setting redis_expiration to 0 turns off expiration