crypto: add deprecation warnings

src/crypto.js

@@ -22,10 +22,12 @@ function sha256(buffer) {
 
 // FIXME: Name not consistent with others
 function HmacSHA256(buffer, secret) {
+  console.warn('Hmac* functions are deprecated for removal in 2.0.0, use node crypto instead')
   return crypto.createHmac('sha256', secret).update(buffer).digest()
 }
 
 function HmacSHA512(buffer, secret) {
+  console.warn('Hmac* functions are deprecated for removal in 2.0.0, use node crypto instead')
   return crypto.createHmac('sha512', secret).update(buffer).digest()
 }