[fix] apply pgDataTypeMapping to changeColumn, closes #2191

lib/dialects/mysql/query-generator.js

@@ -258,7 +258,7 @@ module.exports = (function() {
             template = dataType.type.toString();
           }
 
-          if (dataType.hasOwnProperty('allowNull') && (!dataType.allowNull)) {
+          if (dataType.allowNull === false) {
             template += ' NOT NULL';
           }
 

lib/dialects/postgres/query-generator.js

@@ -181,7 +181,7 @@ module.exports = (function() {
         , sql = [];
 
       for (var attributeName in attributes) {
-        var definition = attributes[attributeName];
+        var definition = this.pgDataTypeMapping(tableName, attributeName, attributes[attributeName]);
         var attrSql = '';
 
         if (definition.indexOf('NOT NULL') > 0) {