Configurable quotes

The transformers currently return both single (addDisplayName and quoteAttrName) and double quotes (JSON.stringify) in the transformed result, so it is impossible to enforce quote rules. I've added an option called useSingleQuotes that decides if double or single quotes should be used throughout. I may be missing other cases, but this seems to address the issues I have had.




They maintain an 80 char limit

```
utils.append(
  'displayName: ' + doubleOrSingleQuotes(displayName, state) + ",",
  state
);
```

Also, inconsistent use of `'` and `"`, we use `'` everywhere it makes sense (but I do know that the JSX source is a bit inconsistent at the moment).