improve BIP32 error message

lib/BIP32.js

@@ -40,7 +40,7 @@ var BIP32 = function(bytes) {
   if (typeof bytes === "string") {
     var decoded = base58.decode(bytes);
     if (decoded.length != 82)
-      throw new Error("Not enough data");
+      throw new Error('Not enough data, expected 82 and received '+decoded.length);
     var checksum = decoded.slice(78, 82);
     bytes = decoded.slice(0, 78);