autoupdate is awesome except it gobbles comments and reformats lists :/

This seems promising: https://pypi.python.org/pypi/ruamel.yaml/0.6

Here's their example:

```
code = ruamel.yaml.load(inp, ruamel.yaml.RoundTripLoader)
code['name']['given'] = 'Bob'
print(ruamel.yaml.dump(code, Dumper= ruamel.yaml.RoundTripDumper), end='')
```
