Update 404 Page. 

The 404 page for invalid application paths was using the old website design, and missing CSS and JS references. Updated the page to the new 404 styling, and updated the redirect links. 

@davideaster, @scottnc27603 Can one of you please review?
Just defines the namespace. According to [W3 Schools](http://www.w3schools.com/tags/att_html_xmlns.asp), it's optional, as it will add it to the HTML tag if not specified. I left it hear to match the index.html page.