Use preset classnames instead of inline style for Responsive design

[cloudinstone]

At present, most styles are implemented by Inline Style, it's not friendly for responsive design. I think it's better to use the Preset Classnames. for example:

= rst rst-theme-{themeName}
== rst-container
=== rst-list
==== rst-item rst-item--depth-{depth} rst-item--has-children rst-item--expanded rst-item--draggable etc.
===== rst-item__header
====== rst-item__handle
====== rst-item__title
===== rst-item__body
==== rst-item rst-item--depth-2 rst-item--collapsed

Keeping css style separated from rendering allows us to have more flexible control for responsive design, and also makes the component code less messy and easier to debug and maintain.