Fix the end slash for DOCTYPE

Steve, we need to add logic in displaying the elements. Just encountered displaying a tag without end an tag in DOCTYPE which displayed as:

<!DOCTYPE html />

which affected some of the CSS display. The DOCTYPE should be rendered as:

<!DOCTYPE html>

One of the HTML5 rules applies to VOID elements such as area, base, br, col, command, embed, hr, img, input, keygen, link, meta, param, source, track, wbr - end slash or "/>" is not needed anymore.

For NON-VOID elements such as A tag for anchoring purpose:

<a id="anchor-id"></a>

should be rendered as:

<a id="anchor-id" />

Another example:

<div class="clearfix"></div>

should be rendered as:

<div class="clearfix" />

I don't know if what I did below is the right thing to do to fix the problem. This request might affect some of the tests in express templates.