Mismatch for normalization b/w docs and code

Re: defining normalization in `recorder.config.json`: in the docs/README it's defined as `normalize` but in [the code](https://github.com/ericclemmons/node-recorder/blob/master/src/Recorder.ts#L511) it's defined as `normalizer`. 

Happy to make a PR for this, but not sure which one is intended to be correct. I guess if we change the code, then there'd have to be a new release, possibly major?