prevent tedious errors from taking down app

Tedious error events must be handled in the connection manager in
order to prevent said errors from crashing an app using sequelize
to connect to a mssql database.

lib/dialects/mssql/connection-manager.js

@@ -47,6 +47,11 @@ ConnectionManager.prototype.connect = function(config) {
     var connection = new self.lib.Connection(connectionConfig);
     connection.lib = self.lib;
 
+    // don't let tedious errors take down the entire application
+    connection.on('error', function(err) {
+      connection._invalid = true;
+    });
+
     connection.on('connect', function(err) {
       if (!err) {
         resolve(connection);