Fix clippy warnings

src/lib.rs

@@ -530,7 +530,7 @@ fn optimize_png(mut png: &mut png::PngData, file_original_size: usize, opts: &Op
         let best: Option<TrialWithData> = results.into_par_iter()
             .weight_max()
             .filter_map(|trial| {
-                let filtered = filters.get(&trial.0).unwrap();
+                let filtered = &filters[&trial.0];
                 let new_idat = if opts.deflate == Deflaters::Zlib {
                         deflate::deflate(filtered, trial.1, trial.2, trial.3, opts.window)
                     } else {

src/main.rs

@@ -452,20 +452,20 @@ fn parse_numeric_range_opts(input: &str,
             return Err("Not a valid input".to_owned());
         }
 
-        return Ok(match &captures[2] {
+        match &captures[2] {
             "," => {
                 items.insert(first);
                 items.insert(second);
-                return Ok(items);
             }
             "-" => {
                 for i in first..second + 1 {
                     items.insert(i);
                 }
-                return Ok(items);
             }
             _ => unreachable!(),
-        });
+        };
+
+        return Ok(items);
     }
 
     Err("Not a valid input".to_owned())

src/png.rs

@@ -485,7 +485,7 @@ impl PngData {
             let mut seen: HashMap<&[u8], u8> = HashMap::with_capacity(indexed_palette.len());
             for (i, color) in indexed_palette.iter().enumerate() {
                 if seen.contains_key(color) {
-                    let index = seen.get(color).unwrap();
+                    let index = &seen[color];
                     duplicates.push(i as u8);
                     index_map.insert(i as u8, *index);
                 } else {