Update to Google Universal Analytics

See also:

 * http://mathiasbynens.be/notes/async-analytics-snippet
 * https://developers.google.com/analytics/devguides/collection/analyticsjs/

Close #109
Remove `IfModule mod_filter.c` check from htaccess

We currently use Apache v2.2.22-14, so the `<IfModule mod_filter.c>`
check isn't necessary. In addition to this, because `mod_filter` isn't
enabled on the server, the check also prevents Apache for compressing
the files.
Update files to reflect the recent changes in H5BP