Swift-SDK - 3.3.1

## 3.3.1
March 30, 2020

### Bug Fixes
* When a datafile download for initialization returns connection errors, the SDK fails to initialize. This is fixed to continue initialization with a cached datafile. ([#308](https://github.com/optimizely/swift-sdk/pull/308))
* Events are not stored persistently in the tvOS devices. ([#310](https://github.com/optimizely/swift-sdk/pull/310), [#311](https://github.com/optimizely/swift-sdk/pull/311))

https://github.com/optimizely/swift-sdk/releases/tag/v3.3.1