[feature]add assets into project

Note: we need to make the images and CSS folders as the style as Rails
pipeline
[chore]use image_tag instead of img tag for index page

Note: we should use Rails way to make the image assets work well
[chore]change all link to link_to current page
[feature]work on about_us page
[refactor]extract header and footer for layout
[chore]reactro on about_us page's header
[feature]add privacy page
[feature]add terms page
[chore]add the triangle_border effect to index page
Merge pull request #7 from peterzd/static_pages

Static pages