Logging-style output doesn't go to stderr

[liamdawson]

Steps

1. stack_master compile ap-southeast-2 ruby_ecr 2>/dev/null >template.yaml

Expected behaviour

template.yaml is a valid YAML file, and can be applied as a CloudFormation template.

Actual behaviour

template.yaml begins with informative output, and is not a valid YAML file.

$ cat template.yaml
- Executing compile on ruby-ecr in ap-southeast-2
Parameters:
...