Javascript-SDK - 2.3.0

## [2.3.0] - November 14, 2018

### New Features
* Allow sticky bucketing via passing in `attributes.$opt_experiment_bucket_map`, this more easily allows customers to do some async data fetching and ensure a user gets a specific variation.

```js
const userId = '123'
const expId = '456'
const variationId = '678'
const userAttributes = {
$opt_experiment_bucket_map: {
[expId]: {
variation_id: variationId
}
}
}

var selectedVariationKey = optimizelyClient.activate('experiment-1', userId, userAttributes);
```

https://github.com/optimizely/javascript-sdk/releases/tag/v2.3.0