js: First testing and improvements

--

* Introduced Mocha/chai as testsuite. After development build
  'npm test' should run the unit tests. Functionality exclusive to
  Browsers/WebExtensions cannot be run this way, so some other testing
  is still needed.

  - package.json: Added required development packages
  - .babelrc indirect configuration for mocha. ES6 transpiling
    needs some babel configuration, but mocha has no setting for it.
  - test/mocha.opts Vonfiguration for mocha runs

* Fixed errors:
  - Helpers.js toKeyIdArray; isLongId is now exported
  - Key.js Key constructor failed
  - Message.js will not throw an Error during construction, a new
    message is now created with createMessage, which can return an
    Error or a GPGME_Message object

* Tests:
  - test/Helpers: exports from Helpers.js, GPGME_Error handling
  - test/Message: first init test with bad parameters

1 files changed, 5 insertions, 2 deletions

diff --git a/lang/js/src/Keyring.js b/lang/js/src/Keyring.js
index e1f0a50f..470eeeec 100644
--- a/lang/js/src/Keyring.js
+++ b/lang/js/src/Keyring.js
@@ -18,7 +18,7 @@
  * SPDX-License-Identifier: LGPL-2.1+
  */
 
-import {GPGME_Message} from './Message'
+import {createMessage} from './Message'
 import {GPGME_Key} from './Key'
 import { isFingerprint, isLongId } from './Helpers';
 import { gpgme_error } from './Errors';
@@ -50,7 +50,10 @@ export class GPGME_Keyring {
      *
      */
     getKeys(pattern, include_secret){
-        let msg = new GPGME_Message('listkeys');
+        let msg = createMessage('listkeys');
+        if (msg instanceof Error){
+            return Promise.reject(msg);
+        }
         if (pattern && typeof(pattern) === 'string'){
             msg.setParameter('pattern', pattern);
         }