Add parens to all lessc mixins

Mixins without parens are deprecated and throwing warnings on
generation.

Author: cpeel

styles/global.less

@@ -87,13 +87,13 @@
 .no-cellpadding {
     border-collapse: collapse;
     td, th {
-        .no-padding;
+        .no-padding();
     }
 }
 
 .plain-list {
     ul {
-        .no-padding;
+        .no-padding();
     }
     li {
         list-style-type: none;