Fully integrate mode tests into main test harness, with extra features.

- Integrated stex and Markdown mode tests into main test harness

- Added ability to restart tests partway through

- Added verbose option, to add message to output for *every* test

- Added ability to show verbose messages and run specific tests or all tests for 1+ mode(s) via location.hash

- Added support for custom messages (either return value [pass] or throw value [fail])

- Switched away from .innerHTML, .write(), etc in most places

- Make the progress bar actually 0px wide when 0% complete (and still keep padding)

- Added link to tests from each mode's demo page

mode/markdown/index.html

@@ -337,5 +337,7 @@ <h1>CodeMirror: Markdown mode</h1>
 
     <p><strong>MIME types defined:</strong> <code>text/x-markdown</code>.</p>
 
+    <p><strong>Parsing/Highlighting Tests:</strong> <a href="../../test/index.html#markdown_*">normal</a>,  <a href="../../test/index.html#verbose,markdown_*">verbose</a>.</p>
+
   </body>
 </html>