type-checking stylesheet functions

is-string, is-keyword, is-color, is-number

lib/less/tree/keyword.js

@@ -13,4 +13,7 @@ tree.Keyword.prototype = {
     }
 };
 
+tree.True = new(tree.Keyword)('true');
+tree.False = new(tree.Keyword)('false');
+
 })(require('../tree'));