[more_notifications]
- make Notification instatiable
- add metric_gauge notification
[more_notifications] send metrics notification on error_rate calculation
- send error_rate
- send success_count
- send failure_count
[more_notifications] warnings
- add Notification#notify_warning
- notify a warning if the sleep window is smaller than the time_window
[more_notifications] force sleep_window to equal time_window if it is
too short.
remove pry-byebug from test_helper
Merge pull request #3 from yammer/more_notifications

More notifications