Centralized resource options

Basically what we talked about in https://github.com/SparkartGroupInc/solidus/pull/74

You have an `auth.json` which contains resource options to be mixed in before requests are made: 

```json
{
	"https://hipster2.sparkart.net/*": {
		"headers": {
			"key": "12345"
		}
	},
	"https://hipster3.sparkart.net/*": {
		"query": {
			"key": "12345"
		}
	}
}
```

And resources are defined as they always have been. You can also define resources with objects from the https://github.com/SparkartGroupInc/solidus/pull/73 branch. Possible resource options are: `headers`, `query`, and `auth`