ability to override default module path

lib/dialects/mysql/connector-manager.js

@@ -4,11 +4,18 @@ var mysql
   , Utils   = require("../../utils")
   , without = function(arr, elem) { return arr.filter(function(e) { return e != elem }) }
 
-try { mysql = require("mysql") } catch (err) {
-  console.log("You need to install mysql package manually"); }
-
 module.exports = (function() {
   var ConnectorManager = function(sequelize, config) {
+    try {
+      if (config.dialectModulePath) {
+        mysql = require(config.dialectModulePath)
+      } else {
+        mysql = require('mysql')
+      }
+    } catch (err) {
+      console.log('You need to install mysql package manually')
+    }
+
     this.sequelize = sequelize
     this.client = null
     this.config = config || {}

lib/dialects/postgres/connector-manager.js

@@ -3,12 +3,14 @@ var Query   = require("./query")
 
 module.exports = (function() {
   var ConnectorManager = function(sequelize, config) {
+    var pgModule = config.dialectModulePath || 'pg'
+
     this.sequelize = sequelize
     this.client       = null
     this.config       = config || {}
     this.config.port  = this.config.port || 5432
     this.pooling      = (!!this.config.poolCfg && (this.config.poolCfg.maxConnections > 0))
-    this.pg           = this.config.native ? require('pg').native : require('pg')
+    this.pg           = this.config.native ? require(pgModule).native : require(pgModule)
 
     // Better support for BigInts
     // https://github.com/brianc/node-postgres/issues/166#issuecomment-9514935

lib/dialects/sqlite/connector-manager.js

-var Utils   = require("../../utils")
-  , sqlite3 = require('sqlite3').verbose()
+var sqlite3
+  , Utils   = require("../../utils")
   , Query   = require("./query")
 
 module.exports = (function() {
-  var ConnectorManager = function(sequelize) {
+  var ConnectorManager = function(sequelize, config) {
     this.sequelize = sequelize
+
+    if (config.dialectModulePath) {
+      sqlite3 = require(config.dialectModulePath).verbose()
+    } else {
+      sqlite3 = require('sqlite3').verbose()
+    }
   }
 
   Utils._.extend(ConnectorManager.prototype, require("../connector-manager").prototype)

lib/sequelize.js

@@ -14,6 +14,7 @@ module.exports = (function() {
     @param {String} [password=null] The password which is used to authenticate against the database.
     @param {Object} [options={}] An object with options.
       @param {String} [options.dialect='mysql'] The dialect of the relational database.
+      @param {String} [options.dialectModulePath=null] If specified, load the dialect library from this path.
       @param {String} [options.host='localhost'] The host of the relational database.
       @param {Integer} [options.port=3306] The port of the relational database.
       @param {String} [options.protocol='tcp'] The protocol of the relational database.
@@ -68,6 +69,7 @@ module.exports = (function() {
 
     this.options = Utils._.extend({
       dialect: 'mysql',
+      dialectModulePath: null,
       host: 'localhost',
       protocol: 'tcp',
       define: {},