Added documentations in source codes
Added jumping between pages

The current number is set in hash in URL, and jumping to specified page in hash
is implemented.
maint: integrated coding style

Integrated the anonymous function style as following:
    function(arg) {
      /* ... */
    }
where there are NO spaces between `function` and `(arg)`.
maint: optimized css and tutorial

First modification is, remove unused style in design.css.  On the other
modification is, the default style of <section> is replaced with styles
in section.contents.  The style section,contents had been removed from
design.css and index.html now.