When an application updates metrics for a toggle we now
stores the timestamp on the toggle when it was last seen
used by an application. This will make it much easier to
detect toggles not in use anymore.
closes#642
Instead of instructing users to do static calls
in to Unleash, she should instead be allwed to
specify the log provider as an option to Unleash.
This commit introduces the "getLogger" option,
a function responsible for creating a logger.
