CSharp-SDK - 3.1.0

May 9th, 2019

### New Features:
* Introduced Decision notification listener to be able to record:
* Variation assignments for users activated in an experiment.
* Feature access for users.
* Feature variable value for users.

### Bug Fixes:
* Feature variable APIs return default variable value when featureEnabled property is false. ([#151](https://github.com/optimizely/csharp-sdk/pull/151))

### Deprecated:
* Activate notification listener is deprecated as of this release. Recommendation is to use the new Decision notification listener. Activate notification listener will be removed in the next major release.

https://github.com/optimizely/csharp-sdk/releases/tag/v3.1.0