Updates CHANGELOG

Author: sdispater

CHANGELOG.md

@@ -7,6 +7,7 @@
 - Added `on()` and `at()` methods which replace `with_date()` and `with_time()`.
 - Added a `strict` keyword argument to `parse()` to get the type matching the parsed string.
 - Added the ability to pass an amount to the `range()` method to control the length of the gap.
+- Added a `datetime()` helper method to the `Timezone` class.
 
 ### Changed