v0.1.8 Release

• Enable de-duplication by default for Sobol Generator
• Improved handling of out-of-design points in Modelbridge
• Use Sobol for small integer spaces in GenerationStrategy (ac91f1d)
• New RayTune tutorial
• Multiple tutorial fixes
• Expose best_point in BotorchModel
• Plotly 4.0 compatibility fixes
• BoTorch 0.2 compatibility