Merge pull request #5025 from dallasread/mysql-browserify

Update MySQL connect manager (browserify fix).

lib/dialects/mysql/connection-manager.js

@@ -14,7 +14,11 @@ ConnectionManager = function(dialect, sequelize) {
   this.sequelize = sequelize;
   this.sequelize.config.port = this.sequelize.config.port || 3306;
   try {
-    this.lib = require(sequelize.config.dialectModulePath || 'mysql');
+    if (sequelize.config.dialectModulePath) {
+      this.lib = require(sequelize.config.dialectModulePath);
+    } else {
+      this.lib = require('mysql');
+    }
   } catch (err) {
     throw new Error('Please install mysql package manually');
   }