* Nitpicky typo fix.
* Grammar / typo fixes.
* Typo fixes.
* Better wording.
* Use one central cleanup timer instead of many concurrently running go functions and timers.
* Fixed unit tests.
* Added a aboutToExpire(key) callback.
* Updated test cases.
* Get rid of helper method.
* Expiration check interval now gets automatically adjusted to the correct (nearest) value.
* Made TestCacheKeepAlive a bit more extensive.
* Be a bit more lax with timer accuracy testing.
* Be a bit more lax with timer accuracy testing.
* Add a few more comments.
* Be a bit more careful with tests.
* Be a godoc comformist.
* Add / fix comments.
* Added a bit more documentation / comments.
* Added (X)CacheCount function, which returns the amount of items in the (x)cache.
* Added a theoretical massive test. Commented out for now.