Rubicon adapter: added sizes (#4147)

* added missing comma

* fixing syntax error

Author: hdeodhar

modules/rubiconBidAdapter.js

@@ -94,7 +94,9 @@ var sizeMap = {
   229: '320x180',
   232: '580x400',
   257: '400x600',
+  264: '970x1000',
   265: '1920x1080',
+  278: '320x500',
   288: '640x380'
 };
 utils._each(sizeMap, (item, key) => sizeMap[item] = key);