uber/clay — pull request #32 by erikformella (2014-03-01 02:35:43+00:00)
Title: Add env variable parsing to yaml config

Often we want to specify certain configs using environment variables
(like on a CI server for instance that generates unique ports for
builds). This adds a special yaml constructor that lets you use this
cute syntax:

```yaml
redis:
port: !env REDIS_PORT or 4444
```