Reading from stdin interrupts at a comment symbol (#)

Hi,

I have a YAML file containing multiple K8s resources. One of the resources contains `data` attribute with a config from a monitoring service. The config has multiple lines commented out with `#` symbol. Running:
```shell
cat production.yaml | docker run --rm -i garethr/kubeval -
```
Validates only first few resources right until the one containing the config. It finishes successfully with error code 0.

Running:
```shell
docker run --rm -v `pwd`:/configs -i garethr/kubeval /configs/production.yaml
```
Correctly validates all the resources.

---

```
docker run --rm -i garethr/kubeval --version
Version: dev
Commit: none
Date: unknown
```