fidian/PrettyCSS — pull request #30 by crowjonah (2014-07-28 17:55:41+00:00)
Title: Skip angle unit checks if value is 0

`addWarning` `'invalid-value'` since unit identifiers are only optional for ``s and expected for ``s (http://www.w3.org/TR/css3-values/#angle-value, https://developer.mozilla.org/en-US/docs/Web/CSS/angle), but don't throw an error.