Merge more testing coverage from henrikingo fork

* core_tests.js and navigation_tests.js have more tests
* qunit_test_runner.html runs QUnit in a browser (without karma) and
  provides a generic iframe based platform to test different  presentations.
* copy qunit.js and syn.js into the repo. This allows qunit_test_runner.html
  to work without any dependency on node/npm. (Karma obviously does need them.)
* Move jscs cli option to .jscsrc instead

test/helpers.js

@@ -0,0 +1,110 @@
+// This file contains so much HTML, that we will just respectfully disagree about js
+/* jshint quotmark:single */
+/* global document, console, setTimeout, navigator */
+/* exported loadIframe, initPresentation, _impressSupported */
+
+var loadIframe = function( src, assert, callback ) {
+  console.log( 'Begin loadIframe' );
+
+  // When running in Karma, the #qunit-fixture appears from somewhere and we can't set its
+  // contents in advance.
+  var fix = document.getElementById( 'qunit-fixture' );
+  fix.innerHTML = [
+    '\n',
+    '    <iframe id="presentation-iframe"\n',
+    '            src="SET THIS IN YOUR QUNIT TESTS"\n',
+    '            width="595" height="485"\n',
+    '            frameborder="0" marginwidth="0" marginheight="0" scrolling="no"\n',
+    '            style="border:1px solid #CCC; max-width: 100%;">\n',
+    '    </iframe>'
+    ].join( '' );
+
+  var iframe = document.getElementById( 'presentation-iframe' );
+
+  var onLoad = function() {
+    assert.ok( true,
+               'Presentation loaded. iframe.src = ' + iframe.src );
+    try {
+      assert.ok( iframe.contentDocument,
+                 'Verifying that tests can access the presentation inside the iframe. ' +
+                 'Note: On Firefox this fails when using paths with "../" parts for the iframe.' );
+    }
+    catch ( err ) {
+      assert.ok( false,
+               'Error when trying to access presentation in iframe. Note: When using Chrome with ' +
+               'local files (file:///) this will fail with SecurityError. ' +
+               'You can however use Chrome over Karma.' );
+    }
+    console.log( 'End loadIframe' );
+    callback();
+  };
+
+  // FIXME: Seems to be some race in loading js files inside the iframe (in CircleCI).
+  // The error that happens is that window.impress isn't set yet, even if onLoad event triggered.
+  // Needs more investigation.
+  var onLoadWrapper = function( event ) {
+    setTimeout( function() { onLoad( event ); }, 1000 );
+  };
+  iframe.addEventListener( 'load', onLoadWrapper );
+
+  assert.ok( true,
+             'Setting iframe.src = ' + src );
+  iframe.src = src;
+};
+
+var initPresentation = function( assert, callback ) {
+  console.log( 'Begin initPresentation' );
+  var iframe = document.getElementById( 'presentation-iframe' );
+  var iframeDoc = iframe.contentDocument;
+  var iframeWin = iframe.contentWindow;
+
+  // Impress:stepenter is the last event triggered in init(), so we wait for that.
+  var waitForStepEnter = function( event ) {
+    assert.ok( true, 'impress (' + event.target.id + ') is now initialized.' );
+    iframeDoc.removeEventListener( 'impress:stepenter', waitForStepEnterWrapper );
+    console.log( 'End initPresentation' );
+    callback();
+  };
+
+  // Unfortunately, impress.js uses the impress:stepenter event internally to
+  // do some things related to entering a step. This causes a race condition when
+  // we listen for the same event and expect it to be done with everything.
+  // We wait 5 ms to resolve the race condition, then it's safe to start testing.
+  var waitForStepEnterWrapper = function( event ) {
+    setTimeout( function() { waitForStepEnter( event ); }, 5 );
+  };
+  iframeDoc.addEventListener( 'impress:stepenter', waitForStepEnterWrapper );
+
+  assert.strictEqual( iframeWin.impress().init(), undefined, 'Initializing impress.' );
+};
+
+// Helper function to determine whether this browser is supported by
+// impress.js or not. Copied from impress.js itself.
+var _impressSupported = function() {
+  var pfx = ( function() {
+    var style = document.createElement( 'dummy' ).style,
+        prefixes = 'Webkit Moz O ms Khtml'.split( ' ' ),
+        memory = {};
+    return function( prop ) {
+      if ( typeof memory[ prop ] === 'undefined' ) {
+        var ucProp  = prop.charAt( 0 ).toUpperCase() + prop.substr( 1 ),
+            props   = ( prop + ' ' + prefixes.join( ucProp + ' ' ) + ucProp ).split( ' ' );
+        memory[ prop ] = null;
+        for ( var i in props ) {
+            if ( style[ props[ i ] ] !== undefined ) {
+                memory[ prop ] = props[ i ];
+                break;
+            }
+        }
+      }
+      return memory[ prop ];
+    };
+  } )();
+
+  var ua = navigator.userAgent.toLowerCase();
+  return ( pfx( 'perspective' ) !== null ) &&
+           ( document.body.classList ) &&
+           ( document.body.dataset ) &&
+           ( ua.search( /(iphone)|(ipod)|(android)/ ) === -1 );
+};
+