Update CHANGELOG to add write_and_append lint

Author: GuillaumeGomez

CHANGELOG.md

@@ -5146,6 +5146,7 @@ Released 2018-09-13
 [`index_refutable_slice`]: https://rust-lang.github.io/rust-clippy/master/index.html#index_refutable_slice
 [`indexing_slicing`]: https://rust-lang.github.io/rust-clippy/master/index.html#indexing_slicing
 [`ineffective_bit_mask`]: https://rust-lang.github.io/rust-clippy/master/index.html#ineffective_bit_mask
+[`ineffective_open_options`]: https://rust-lang.github.io/rust-clippy/master/index.html#ineffective_open_options
 [`inefficient_to_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#inefficient_to_string
 [`infallible_destructuring_match`]: https://rust-lang.github.io/rust-clippy/master/index.html#infallible_destructuring_match
 [`infinite_iter`]: https://rust-lang.github.io/rust-clippy/master/index.html#infinite_iter