Support for reload, style improvements

- reload the present., keep the current slide on SPC
  => useful for previewing it while developing it
- moved the background div to the background
 not to prevent copying and clicking on the content
- style: brownish color for code to make it stand out
- readme improvements
Updated Showdown to 0.3.1, info about Sh. extensions

- updated to 0.3.1
- added info about custom and existing Showdown extensions
- links to related tools (PageDown, reveal.js)
Merge pull request #1 from jakubholynet/master

Support for live reloading, Showdown upgrade, fixes etc.
Basic Windows install instructions added.
Better readability.
Merge pull request #2 from steenhulthin/windows_install

Windows install
Presentation is now possible when offline (if the webserver is local).
Merge pull request #3 from steenhulthin/offline_support

Presentation is now possible when offline (if the webserver is local).
Add printing support.
- Then, we can print to PDF printer and publish the PDF to slideshare.com.
Merge pull request #4 from jsakamoto/feature/printing

Add printing support.
Support for mobile device and touch-ready OS such as iPhone/iPad/Android/Windows8
- Swipe operation support for touch device.
- Multi screen resolution support by using CSS media query.
- Hide address bar automatically on mobile device.
Fix: Printing dose not work on Google Chrome.
- Because Google Chrome not support 'beforeprint' event. Build pages for printing immediately after mark down loaded if 'beforeprint' event does not provided.
Merge pull request #6 from jsakamoto/fix/print-not-work-on-chrome

Fix: Printing dose not work on Google Chrome.
Merge pull request #5 from jsakamoto/feature/mobiledevice

Support for mobile device and touch-ready OS such as iPhone/iPad/Android/Windows8
Fix the problem that does not work well reloading feature (space key) at some browser or environment.
Add 'go to page' feature.
- Hash of URL indicate current slide index, and when hash of URL changed then show the slide which specified by hash.
- 'Slide n of m' change from static text to drop down list.
- PowerPoint compatible keyboard shortcut: press some numeric key and enter, for example, '2','1',[Enter], then show the slide page 21.
Fix: jQuery .js file does not load from CDN at SSL access & ran into security violation.
- Change the URL of jQuery .js file from absolute URL to network-path reference URL. [http://tools.ietf.org/html/rfc3986#section-4.2]
Merge pull request #7 from jsakamoto/fix/fail-jqload-at-ssl

Fix: jQuery .js file does not load from CDN at SSL access & ran into security violation.
Merge pull request #8 from jsakamoto/fix/reload_issue

Fix the problem that does not work well reloading feature (space key) at some browser or environment.
Merge pull request #9 from jsakamoto/feature/goto_page

Add 'go to page' feature.