Space after keywords superset rule (nested required/allowed)

# DO NOT MERGE

Sample aggregate rule example from #136

```js
"spaceAfterKeywords": {
  "required": ["if"],
  "disallowed": ["return"]
}
```

TODO:

 - [ ] How to map old rule back in given current export pattern
 - [ ] How to deal with conflicting keys? i.e.: keyword that is in both allowed and disallowed

/cc @marklog