Add mixin for transition-property

It's quite handy if a transition needs the same duration, timing-function or delay and only specific properties to animate.

less/mixins.less

@@ -112,6 +112,10 @@
   -webkit-transition: @transition;
           transition: @transition;
 }
+.transition-property(@transition-property) {
+  -webkit-transition-property: @transition-property;
+          transition-property: @transition-property;
+}
 .transition-delay(@transition-delay) {
   -webkit-transition-delay: @transition-delay;
           transition-delay: @transition-delay;