Merge pull request #36 from zenozeng/master

Use prop('scrollWidth') and prop('scrollHeight') instead of outerWidth() and outerHeight() to get the content size.
Remove $content.

It's not used anymore.
Modify README.md.

The requirement that force just one content element is gone.
JSHint the code.

Missing space.
Fix the wrong indents in example pages.
Inhance the scroll logic with mobile touches.

The scroll works only when the user touch and scroll the wrapper div
with just one touch. By this patch, the zoom function will not be
prevented by scrolling content.
Refactor jshint files.

We'll use grunt, and jshintignore is useless.
Remove comments in jshintrc to be parsed in grunt.
Add node_modules in gitignore.
Remove build shell script.

We'll use grunt to build the scripts.
The shell script is no more used.
Csslint the css file.
Add csslintrc.
Add files for Grunt.
Minify source files with the new build system.

From now, the build can be done with 'grunt build'.
Update README.

The link to Contributing wiki page is added.
Add a sample based on text content
Add feature to suport ie.

For ie browser, the `.ps-container` element will add extra class `ie`
and `ie<version>`, like `ie6`, `ie7`, `ie8`, etc.
Add hover handlers for ie6.

Use scripts to add '.hover' class on the `.ps-container` and both
scrollbars when then mouse is over them because :hover is not supported
except 'a' element.
Fixed the scrollbar height for xp sp3 ie6

set 'font-size:0' for the scrollbar
Separate the function updating the css of scrollbars.
Fix ie6 scrollbar position problem.

This patch is in fact contributed by the idea of @maoziliang.