Parse out ENV variables from config.json

Examples:

(Heroku)
```json
{
	"siteIP": {"ENV": "IP"},
	"sitePort": {"ENV": "PORT"},
	"db": {
        "type":"mongo",
		"servers": [{"ENV": "MONGOHQ_URL"}],
        "name": "pencilblue",
        "writeConcern": 1
	}
}
```
(Openshift)
```json
{
	"siteIP": {"ENV": "OPENSHIFT_NODEDIY_IP"},
	"sitePort": {"ENV": "OPENSHIFT_NODEDIY_PORT"},
	"db": {
        "type":"mongo",
		"servers": [{"ENV": "OPENSHIFT_MONGODB_DB_URL"}],
        "name": {"ENV" "OPENSHIFT_APP_NAME"},
        "writeConcern": 1
	}
}
```