Go-SDK - v0.2.0

## [0.2.0] - September 11th, 2019
This release of the SDK introduces Feature Management capabilities for running both Feature Rollouts as well as Feature Tests using Optimizely Feature Management.

### New Features
- Introduces feature variable getters via `GetFeatureVariable*` for parameterizing your feature tests.
- Introduces the `Track` API call for sending conversion events to Optimizely.
- The `IsFeatureEnabled` API will now send impression events if there is a feature test attached to the feature being accessed.

### Breaking Changes
- Vendored packages have been removed in favor of declaring dependencies and their versions using `go.mod`.