responsive navbar

The navbar now is responsive. Custom javascript is added to highlight
the active navtab. (However it's less blue now)

modified:   _includes/banner.html
modified:   _includes/header.html
modified:   _includes/javascript.html
modified:   _layouts/people.html
modified:   css/blog.css
modified:   people/index.html

Signed-off-by: Yishen Miao <mys721tx@gmail.com>
Added example banner image
Update 2014-03-01-gnome-studies.markdown
css banner image, style fix, naked excerpt, sidebar fix

Change the banner to css background with linear gradient so it will be
in the same style the rest of the blog is.

Add some style fix to many pages.

The index now will only show naked html from posts.

A unmatched div is fixed in _includes/sidebar.html.

modified:   _includes/banner.html
modified:   contact.html
modified:   css/blog.css
modified:   index.html
modified:   prospective-student.html
modified:   _includes/sidebar.html
modified:   index.html