Initial implementation of schemas

Still lacks more tests as well as actual schema validation. Follows the format from #9:

```json
{ 
  "aws": {
    "secret": "dfsjhhgdfshkdfshjkfds",
    "description": "This is my secret for xxxx",
    "type": "AWS|SSH|SSL|PASSWORD|TOKEN|OAUTH|OTHER",
    "severity": "LOW|MED|HIGH",
    "rotation": "To rotate this secret, clone the account <current account name>. Create a new secret. Then ..",
    "urls": ["https://aws.amazon.com"]
  }
}
```

@burke @dalehamel