internals(and/or) Fix use of plain or and and internally for pg

lib/dialects/abstract/query-generator.js

@@ -1885,6 +1885,11 @@ var QueryGenerator = {
       if (typeof value === 'string') {
         return value;
       }
+
+      if (_.isPlainObject(value) && _.size(value) === 1) {
+        key = Object.keys(value)[0];
+        value = _.values(value)[0];
+      }
     }
 
     if (value && value._isSequelizeMethod && !(key !== undefined && value instanceof Utils.fn)) {
@@ -1899,19 +1904,16 @@ var QueryGenerator = {
         return Utils.format(value, this.dialect);
       }
     }
-
     // OR/AND/NOT grouping logic
     if (key === '$or' || key === '$and' || key === '$not') {
-
       binding = (key === '$or') ?' OR ' : ' AND ';
-
       outerBinding = '';
       if (key === '$not') outerBinding = 'NOT ';
 
       if (Array.isArray(value)) {
         value = value.map(function (item) {
           var itemQuery = self.whereItemsQuery(item, options, ' AND ');
-          if ((Array.isArray(item) || _.isPlainObject(item)) &&_.size(item) > 1) {
+          if ((Array.isArray(item) || _.isPlainObject(item)) && _.size(item) > 1) {
             itemQuery = '('+itemQuery+')';
           }
           return itemQuery;