The old behaviour will override child option nodes like options.client, causing properties to be lost if the new
option node is only partially specified. This partially causes karma-runner/grunt-karma#165 and
karma-runner/grunt-karma#166.

Was:

```js
var stopper = require('karma').stopper
runner.stop({port: 9876}, function(exitCode) {
```

Changed to :

```js
var stopper = require('karma').stopper
stopper.stop({port: 9876}, function(exitCode) {
```

fix(docs): fix stopper.stop wrong variable name. closes #2244

fix: Merge config files on Config.set()

…ma messages

… promise.then

Closes #2227

fix WARN logs for undefined error handler

Thanks to @m-a-r-c-e-l-i-n-o for pointing me in the right direction
Fixes #2194

…shed

fix(context): Updated postMessage listener to stop validating non-Karma messages

fix(file-list): ensure patterns are comparable