"Critical dependency: the request of a dependency is an expression" with webpack, Babel & TypeScript

**Describe the bug**
I am using a TypeScript setup with webpack and babel and get the following warnings when including `elastic-apm-node`.

```
WARNING in node_modules/elastic-apm-node/lib/agent.js 152:16-59
Critical dependency: the request of a dependency is an expression
@ node_modules/elastic-apm-node/index.js

WARNING in node_modules/elastic-apm-node/lib/config.js 25:19-36
Critical dependency: the request of a dependency is an expression
@ node_modules/elastic-apm-node/lib/agent.js

WARNING in node_modules/elastic-apm-node/lib/instrumentation/index.js 169:16-30
Critical dependency: the request of a dependency is an expression
@ node_modules/elastic-apm-node/lib/agent.js
```

**To Reproduce**
Steps to reproduce the behavior:
1. Clone https://github.com/arichter83/meteor-webpack/tree/with-elastic-apm-node
2. Run `npm install`
3. Run `npm start`

**How are you starting the agent? (please tick one of the boxes)**
- [x] Requiring `elastic-apm-node/start` from within the source code