CSharp-SDK - 3.5.0

- Add support for JSON feature variables. ([#214](https://github.com/optimizely/csharp-sdk/pull/214), [#216](https://github.com/optimizely/csharp-sdk/pull/216), [#217](https://github.com/optimizely/csharp-sdk/pull/217)) - Add support for authenticated datafiles. ([#222](https://github.com/optimizely/csharp-sdk/pull/222)) - Add gzip support for framework 4.5 or above. ([#218](https://github.com/optimizely/csharp-sdk/pull/218))

- Adjust audience evaluation log level to debug. ([#221](https://github.com/optimizely/csharp-sdk/pull/221))

https://github.com/optimizely/csharp-sdk/releases/tag/v3.5.0