Request/Session attribute binding. fixes #9

Our project uses spring-jade4j.
Spring-jade4j does not regard **HttpServletRequest/HttpSession attributes** as model attributes.
But we have to use a lot of attributes which are injected into request/session from filters and interceptors.

This patch just change the parent classes.
For JadeView, the parent is changed from AbstractUrlBasedView to **AbstractTemplateView**.
For JadeViewResolver, the parent is changed from UrlBasedViewResolver to **AbstractTemplateViewResolver**.

After this patch, org.springframework.web.servlet.support.RequestContext also can be exposed as a model attribute. This can be used for spring theme, locale, messageSource and url handling, etc..