A little suggestion for styles

[joelself]

Stolen from zenorocha#42

The box looks strange on pages with CSS resets like this:

* { box-sizing: border-box; }

This is used quite often as far as I know.
So I suggest this to be added to base.css:

.github-box .github-box-download {
  // ...
  box-sizing: content-box;
}