:hide_success shows success notification after a failure

The :hide_success previously prevented all notification of success. This commit makes guard-coffeescript notify of a successful run after a failure or failures, even with :hide_success set to true. This conforms to a standard pattern of notification of success after failure (an "all clear" notification).

Before this change, when using the terminal_notifier, the terminal title would continue to show an error message even after the error had been fixed and there had been a successful compile.

(Also fixed some awkward grammar in one of the spec names.)