[Update] Improve slugify()'s set of invalid characters.

util.go

@@ -85,9 +85,17 @@ func normalizedFileExt(filename string) string {
 	return strings.ToLower(ext[1:])
 }
 
+// Returns a trimmed and encoded slug of the passed string that should be safe
+// for use as a DOM ID or class name.
 func slugify(original string) string {
-	// TODO: Maybe expand this to include non-ASCII alphas?
-	invalidRe := regexp.MustCompile(`[^[:word:]-]`)
+	// NOTE: The range of illegal characters consists of: C0 controls, space, exclamation,
+	// double quote, number, dollar, percent, ampersand, single quote, left paren, right
+	// paren, asterisk, plus, comma, hyphen, period, forward slash, colon, semi-colon,
+	// less-than, equals, greater-than, question, at, left bracket, backslash, right
+	// bracket, caret, backquote/grave, left brace, pipe/vertical-bar, right brace, tilde,
+	// delete, C1 controls.
+	invalidRe := regexp.MustCompile(`[\x00-\x20!"#$%&'()*+,\-./:;<=>?@[\\\]^\x60{|}~\x7f-\x9f]+`)
+
 	return strings.ToLower(invalidRe.ReplaceAllLiteralString(original, "-"))
 }