Use shorter charset <meta>

See <http://mathiasbynens.be/notes/html5-levels#level-1>. Also move it to right above the `<title>` as per <https://github.com/h5bp/html5-boilerplate/blob/master/doc/html.md#the-order-of-meta-tags-and-title>.

I ended up making the HTML response more minimal in general by omitting optional start and end tags, etc.