Copy ox-html.el to ox-html5presentation.el.
Rename prefix to org-html5presentation from org-html.

* and rename ox-html to ox-html5presentation.
Modify backend definition.
Change doctype to html5.
Add a meta tag X-UA-Compatible.
Change style tag.

Change org-html5presentation-style-default contents.
Remove :html-head-include-scripts option.

Remove it from backend definition and remove a line that option used.
Add org-html5presentation-divs.

Add `flex-container' and `slides' and remove `content'.
Remove `Document title'.
Add a help section.

Add org-html5presentation-helpers is a customizable variable has
help contents describe usage of the HTML5 Presentation slides.
Disable toc.
Add org-html5presentation-loading.

Add org-html5presentation-loading is a customizable variable for
loading message will be shown when contents are loading.

Move org-html5presentation-helpers call into org-html5presentation-template.
Add template variables.

* org-html5presentation-ie-lt-9-js
  JavaScript template for IE less than version 9.

* org-html5presentation-prettify-js
  JavaScript template for prettify.js.

* org-html5presentation-util-js
  JavaScript template for util.js.
Correspond to HTML5 slide format.

* Use header tag to Org headline
* Use section tag to Org section
Add org-html5presentation-title-slide.
Remove calls for preamble and postamble.
Fix typo org-html5presentation-title-slide.
Rename org-html5presentation-helpers to org-html5presentation-navi.
Add org-html5presentation-help.
Change to prevent section nesting.