Added option for default global transaction isolation level.

Updated doc about contributing.

CONTRIBUTING.md

@@ -141,10 +141,11 @@ $ DIALECT=dialect SEQ_DB=database SEQ_USER=user SEQ_PW=password make test
 ```
 
 #### 4a. Check the documentation
-This step only applies if you have actually changed something in the documentation. To generate documentation for the `sequelize.js` file, run (in the sequelize dir)
+This step only applies if you have actually changed something in the documentation. Please read `CONTRIBUTING.DOCS.md` first.
+To generate documentation for the `sequelize.js` file, run (in the sequelize dir)
 
 ```console
-$ node docs/markdox.js --file lib/sequelize.js
+$ npm run docs
 ```
 
 The generated documentation will be placed in `docs/tmp.md`.

lib/sequelize.js

@@ -83,8 +83,8 @@ module.exports = (function() {
    * @param {Integer}  [options.pool.minConnections]
    * @param {Integer}  [options.pool.maxIdleTime] The maximum time, in milliseconds, that a connection can be idle before being released
    * @param {Function} [options.pool.validateConnection] A function that validates a connection. Called with client. The default function checks that client is an object, and that its state is not disconnected
-
    * @param {Boolean}  [options.quoteIdentifiers=true] Set to `false` to make table names and attributes case-insensitive on Postgres and skip double quoting of them.
+   * @param {String}   [options.isolationLevel='REPEATABLE_READ'] Set the default transaction isolation level. See `Sequelize.Transaction.ISOLATION_LEVELS` for possible options.
   */
 
   /**
@@ -146,7 +146,8 @@ module.exports = (function() {
       ssl: undefined,
       pool: {},
       quoteIdentifiers: true,
-      hooks: {}
+      hooks: {},
+      isolationLevel: Transaction.ISOLATION_LEVELS.REPEATABLE_READ
     }, options || {});
 
     if (this.options.dialect === 'postgresql') {
@@ -1111,7 +1112,7 @@ module.exports = (function() {
 
    * @param {Object} [options={}]
    * @param {Boolean} [options.autocommit=true]
-   * @param {String} [options.isolationLevel='REPEATABLE READ'] See `Sequelize.Transaction.ISOLATION_LEVELS` for possible options
+   * @param {String} [options.isolationLevel='REPEATABLE_READ'] See `Sequelize.Transaction.ISOLATION_LEVELS` for possible options
    * @return {Promise}
    * @fires error If there is an uncaught error during the transaction
    * @fires success When the transaction has ended (either comitted or rolled back)

lib/transaction.js

@@ -14,7 +14,7 @@ var Transaction = module.exports = function(sequelize, options) {
   this.savepoints = [];
   this.options = Utils._.extend({
     autocommit: true,
-    isolationLevel: Transaction.ISOLATION_LEVELS.REPEATABLE_READ
+    isolationLevel: sequelize.options.isolationLevel
   }, options || {});
   this.id = this.options.transaction ? this.options.transaction.id : Utils.generateUUID();
 
@@ -29,7 +29,9 @@ var Transaction = module.exports = function(sequelize, options) {
 };
 
 /**
- * The possible isolations levels to use when starting a transaction
+ * The possible isolations levels to use when starting a transaction.
+ * Can be set per-transaction by passing `options.isolationLevel` to `sequelize.transaction`.
+ * Default to `REPEATABLE_READ` but you can override the default isolation level by passing `options.isolationLevel` in `new Sequelize`.
  *
  * ```js
  * {