Version 3.0 published

• Switched to using Nito.AsyncEx for synchronization context. This is required for console applications to use async/await without corrupting the console output. (see https://devblogs.microsoft.com/dotnet/await-synchronizationcontext-and-console-apps/ for details)
• Changed WriteSpinner() => StartSpinner() to better reflect the usage of the spinner. This gets rid of janky lock(Console.Out)
• Added additional method overloads for animation and success/failed to make it easier to invoke
• updated readme