Tweak <code> layout

Closed username-removed-24982 requested to merge eighthave/fdroid-website:tweak-code-layout into master

The example pages that use large <code> blocks are often too wide, pushing the right-nav far right. I'm sure there is a better way to handle this, but I suck at CSS. This is two simple fixes that improves things quite a bit. If someone knows a better way, I'd love to see something rather than this.

@NicoAlt @fxedel