remove debug code

src/encoder.rs

@@ -43,7 +43,6 @@ fn encode_body (header: Header, data: &[u8]) -> Option<Vec<u8>> {
     let mut last = [0u8, 0, 0, 255];
     let mut out = vec![];
     let mut cur = Ops::Nop;
-    let mut counter = 0;
 
     for mut chunk in &data.iter().chunks(header.channels.num()) {
         let (&r, &g, &b) = chunk.next_tuple()?;