Support for loading YAML files

[weibeld]

I couldn't find any facilities in this library to load Kubernetes API objects from YAML files, something like this for the Java client.

Currently, I have to do it like this with js-yaml and fs:

const yaml = require('js-yaml');
const fs = require('fs');

const deployment = yaml.safeLoad(fs.readFileSync('deployment.yml', 'utf8'));

// ...in order to use it for:
apiClient.createNamespacedDeployment('default', deployment, true);

Maybe it would be good to have a class for this, like in the Java client, or at least mention it in the README how it can be done with js-yaml.

[brendandburns]

I'll add this support.