Added a changelog entry.

Author: hicklin

CHANGELOG.md

@@ -40,6 +40,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Added implementation of `Borrow` and `BorrowMut` for `String` and `Vec`.
 - Added `Deque::{swap, swap_unchecked, swap_remove_front, swap_remove_back}`.
 - Make `String::from_utf8_unchecked` const.
+- Implemented `PartialEq` and `Eq` for `Deque`.
 
 ### Changed