v0.4.1

• Fixed a bug that caused green to red notifications to sometimes not be sent.

v0.4.0

• Made stoplights handle failing notifiers by logging the failure to standard
  error.
• Made stoplights automatically fall back to a fresh in-memory data store if the
  primary store is unavailable.
• Generalized Stoplight::Notifier::StandardError into
  Stoplight::Notifier::IO.
• Changed notification format from a string to a lambda. It accepts the same
  parameters that the format string accepted.
• Updated Stoplight::Notifier::Base#notify to accept three parameters (the
  light, the before color, and the after color) instead of just one parameter
  (the message).
• Prevented setting non-positive thresholds.
• Removed Stoplight::Mixin.

v0.3.1

• Replaced Stoplight::Failure#error with #error_class and #error_message.
  Also changed the constructor to take the class and the message instead of the
  error.

v0.3.0

• Allowed formatting notifications.
• Added automatic recovery from red lights.
• Added Stoplight::DataStore#clear_stale for clearing stale lights.
• Removed forwarded methods on Stoplight module.
• Moved some methods from Stoplight::DataStore::Base to
  Stoplight::DataStore.
• Renamed Stoplight::DataStore::Base#purge to #clear_stale.
• Renamed Stoplight::DataStore::Base#delete to #clear.
• Prefixed data store getters with get_.
• Added Stoplight::DataStore::Base#sync.
• Changed Stoplight::DataStore::Base#get_failures to return actual failures
  (Stoplight::Failure) instead of strings.

v0.2.1

• Forced times to be serialized as strings.

v0.2.0

• Switched Stoplight.data_store and Stoplight.notifiers over to using
  simple accessors.
• Modified Stoplight::DataStore::Redis to accept an instance of Redis.
• Refactored Stoplight::DataStore::Redis to use fewer keys.
• Created Stoplight::Notifier and subclasses.
• Sent notifications when moving from green to red.
• Renamed Stoplight::Light::DEFAULT_THRESHOLD to
  Stoplight::DEFAULT_THRESHOLD.
• Renamed Stoplight::Error::NoFallback to Stoplight::Error::RedLight.
• Created Stoplight::Mixin#stoplight for easily creating and running simple
  stoplights.

v0.1.0

• Initial release.