JSON & Standalone version

This switches back to JSON for the data format. Being a node.js project it seems better to use a natively supported format by default and allow people who want another format, such as YAML, to provide support for it themselves. This pull request also refactors slightly to allow for a standalone version of the library that can be used in the browser. The standalone version can be built using `make standalone` with the desired locale files specified in the `LOCALES` environment variable:

```
$ LOCALES="lib/locales/en.json lib/locales/en-us.json /path/to/custom/is.json" make standalone
```

Which will create `build/charlatan.standalone.js`.