Racer 2

[craigbeck]

racer@2 breaking changes:

• The Model class should no longer be directly constructed. Use createModel() instead.
  • For example, new racer.Model() -> racer.createModel()
  • Directly trying to construct Model can result in errors like Cannot set properties of undefined (setting 'socket') from Model.createConnection
• racer no longer and instance. racer now a proper namespace
• legacy event handlers not supported by typescript
• Drop support for node 10-14
• remove deprecated getModel() method form req object in modelMiddleware