Made ring optional

src/lib.rs

@@ -1,6 +1,5 @@
 #![no_std]
 #![allow(stable_features)]
-#![feature(alloc)]
 
 extern crate alloc;
 
@@ -8,5 +7,9 @@ mod aead;
 mod dh;
 mod kdf_root;
 mod kdf_chain;
-mod header;
+
+/// Providing essential functions
 pub mod ratchet;
+
+/// Message Header
+pub mod header;