Removed Google CDN reference for jQuery

http://statichtml.com/2011/google-ajax-libraries-caching.html

According to that, there is a very little benefit to using the
Google CDN to serve jQuery source.  A better option would be to
encourage devs to minify and concatenate all of their script files
into one JS file served with a long-lived cache time.

This was referenced by Alex Sexton (@SlexAxton) in his talk at
jQueryTO March 2nd, 2013.

Also:
* Included the unminified version of jQuery
* Included the jQuery source map file (in the /js/vendors folder)
* Added a reference to the jQuery source map file in the minified jQuery file
* Included a line about the change in the CHANGELOG
Merge branch 'removeCDN' of https://github.com/localpcguy/html5-boilerplate into removeCDN