Writer implementation

creaet_frame_buffer() interface has been moved to WaveFmt

src/wavereader.rs

@@ -28,7 +28,7 @@ use std::io::{Read, Seek};
  * assert_eq!(format.channel_count, 1);
  * 
  * let mut frame_reader = r.audio_frame_reader().unwrap();
- * let mut buffer = frame_reader.create_frame_buffer();
+ * let mut buffer = format.create_frame_buffer();
  * 
  * let read = frame_reader.read_integer_frame(&mut buffer).unwrap();
  *