removed classes from section elements 2

the last commit didn't actually do that.  Also, I removed a superfluous
div
added a row to the section "top"

I changed span8 to span9 since the sidenav only takes up 3 grid spans
out of 12 possible.  I added a row div with span4 and span5 to equal
span9.  Everything is working now!
removed snippets section

I removed the snippets link, since I don't have a snippets html anymore
after posting this on Github.
removed masthead pattern, localized css files

commented out reference to bs-docs-masthead-pattern.png, so the
jumbotron is now just a plain gradient.  Also, I changed index.html to
use the local css files instead of the css files on twitter's servers.