We should bubble up pump errors

https://github.com/godaddy/kubernetes-client/blob/master/backends/request/client.js#L179

For some local debugging of the watch example I just did the following which surfaced my error:

```js
pump(stream, jsonStream, (err) => {throw err})
```

Aside: The following issue might be deprecated with the new getObjectStream stuff: https://github.com/godaddy/kubernetes-client/issues/248?

Start in backends/request/client.js around line 179 and inspect how pump errors are handled for the watch example. Check issue #248 and the newer getObjectStream behavior before making changes; done means errors from pump are surfaced rather than silently lost.

Written by the indexing model from the issue text.