Add failing test to illustrate bug with markdown-to-draft

Disabled the failing test so that specs still pass, but keep it in place to remind us that it should be resolved.

The bug is that in cases when someone has a multi-line blockquote with blank lines, markdown generated should have empty `>` lines, but it instead simply strips those lines.

test/idempotency.spec.js

@@ -79,6 +79,15 @@ describe('idempotency', function () {
     expect(markdownFromDraft).toEqual(markdownString);
   });
 
+  // TODO this test should pass but markdown-to-draft doesn’t correctly create empty markdown blocks in this case currently.
+  xit('renders blockquotes with blank lines correctly', function () {
+    var markdownString = '> Hello I am Blockquote\n> more\n> \n> \n> hey';
+    var draftJSObject = markdownToDraft(markdownString);
+    var markdownFromDraft = draftToMarkdown(draftJSObject);
+
+    expect(markdownFromDraft).toEqual(markdownString);
+  });
+
   it('renders links correctly', function () {
     var markdown = 'This is a test of [a link](https://google.com)\n\nAnd [perhaps](https://facebook.github.io/draft-js/) we should test once more.';
     var rawDraftConversion = markdownToDraft(markdown);