codec: rename kind() to medium()

src/codec/context.rs

@@ -45,7 +45,7 @@ impl<'a> Context<'a> {
 		}
 	}
 
-	pub fn kind(&self) -> media::Type {
+	pub fn medium(&self) -> media::Type {
 		unsafe {
 			media::Type::from((*self.ptr).codec_type)
 		}