Preserve sensitive whitespace

[mcandre]

Some HTML elements render differently depending on extra spaces. This can happen with <pre>, <tt>, <kbd>, <span>, and so on. For inner HTML on these kinds of DOM elements, please leave the original whitespace as-is.

breezewish/express-minify#12 (comment)

For <span> elements in particular, designers are ill-advised to use leading or trailing whitespace in inner HTML. Perhaps jade-compress could emit a console warning when such extra space is found. Though again, this should be preserved until the designer gets around to accounting for styling the page properly once the space is manually removed.