add documentation

Author: Guanqun Lu

CHANGELOG.md

@@ -1173,6 +1173,7 @@ Released 2018-09-13
 [`replace_consts`]: https://rust-lang.github.io/rust-clippy/master/index.html#replace_consts
 [`result_expect_used`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_expect_used
 [`result_map_unit_fn`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_map_unit_fn
+[`result_map_unwrap_or`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_map_unwrap_or
 [`result_map_unwrap_or_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_map_unwrap_or_else
 [`result_unwrap_used`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_unwrap_used
 [`reverse_range_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#reverse_range_loop

README.md

@@ -6,7 +6,7 @@
 
 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
 
-[There are 333 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+[There are 334 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
 
 We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you: