clean up decode_named_entity

Update the code style to current Rust.
Add the proper license notice to the entity.rs file.

src/entity.rs

@@ -1,3 +1,28 @@
+/*
+The below piece of code was taken from:
+https://github.com/veddan/rust-htmlescape/blob/master/src/entities.rs
+
+Copyright 2016 Viktor Dahl <pazaconyoman@gmail.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
 pub static ENTITIES: &'static [(&'static str, char)] = &[
     ("AElig", '\u{00C6}'),
     ("AMP", '\u{000026}'),

src/lib.rs

@@ -3,15 +3,11 @@
 mod entity;
 
 const LBR: &str = "\r\n";
-// stolen from https://github.com/veddan/rust-htmlescape/blob/master/src/decode.rs
 fn decode_named_entity(entity: &str) -> Option<char> {
-    match entity::ENTITIES.binary_search_by(|&(ent, _)| ent.cmp(entity)) {
-        Err(..) => None,
-        Ok(idx) => {
-            let (_, c) = entity::ENTITIES[idx];
-            Some(c)
-        }
-    }
+    entity::ENTITIES
+        .binary_search_by_key(&entity, |t| t.0)
+        .map(|idx| entity::ENTITIES[idx].1)
+        .ok()
 }
 
 const BAD_TAGS: [&str; 4] = ["head", "script", "style", "a"];