Closes #1163, #1495.

Switching a `display: block` element to `display: inline-block` allows calculating the bounds based on the contents of the div rather than the entire container (which is often `width: 100%`).

This provides a much more natural zoom, especially for paragraphs and code examples.

Closes #1392.

In html content, marked allow `Inline-Level Grammar` but not `Block-Level Grammar`, so when I write following:
```
note:
* a
* b
* c
```
it become:
```html
<p><em> a
</em> b</p>
<ul>
<li>c</li>
</ul>
```
unbelievable!

Just using $ as delimiter in markdown document fails since the markdown
parser unknown to the dollar syntax will try to interpret underscores.
Putting the $ delimented formula in backticks will cause the markdown
parser to put the tex-code with the $ delimiters into a code block.
The texcode will then be unchanged. This patch allows for mathJax to
interpret and automagically display the tex-formulas.

by changing the tag before html is parsed and restoring it before markdown parsing

Compressed with `uglifyjs lib/marked.js --comments="/Copyright/" --mangle --compress`

Used Marked v0.3.3 as of chjj/marked@2b5802f258c5e23e48366f2377fbb4c807f47658

see https://github.com/hakimel/reveal.js/issues/929#issuecomment-80738837