Karma Unit Test Failures: Cannot find 'babel-plugin-instanbul'

**I'm submitting a bug report**

* **Library Version:**
1.0.0-beta.9

**Please tell us about your environment:**
* **Operating System:**
Windows 10

* **Node Version:**
8.9.0

* **NPM Version:**
6.5.0

* **Browser:**
Chrome / All

* **Language:**
ESNext

* **Loader/bundler:**
Webpack

**Current behavior:**
Karma tests fail to run with the following error:

> Error: Cannot find module 'babel-plugin-istanbul' from 'C:\Users\xxx\Documents\aurelia_cli_2019\cli\aurelia-starter-test'
> If you want to resolve "istanbul", use "module:istanbul"

I found this issue: https://github.com/aurelia/cli/issues/996 and saw that the latest karma-webpack version is incorrect, so I installed "4.0.0-rc.3" as suggested. This did not fix the issue. I also noticed someone mentioned that the following would need to be added to karma.conf.js, but this also did not fix the issue:

```module.exports = function (config) {
config.set({
...
coverageIstanbulReporter: {
...
skipFilesWithNoCoverage: true
},
})
}
```

* **What is the expected behavior?**

Tests should successfully run

* **What is the motivation / use case for changing the behavior?**
I'm trying to upgrade my aurelia project from webpack 3 to webpack 4, but since the aurelia skeleton isn't up to date, and the aurelia-cli is broken, I don't have a valid setup to reference.