Sheller 5.1.1

This release changes:

• N/A.

This release adds:

• WithCancellationToken to IShell and IExecutable.
• ConfigureAwait(false) to all awaits.
• A bunch more examples to the README.

WithCancellationToken allows the developer to provide cancellation tokens to the execution context.

using (var ctSource = new CancellationTokenSource())
{
    ctSource.CancelAfter(TimeSpan.FromSeconds(5));

    Builder
        .UseShell<Bash>()
        .UseExecutable<Sleep>()
        .WithArgument("5")
        .WithCancellationToken(ctSource.Token)
        .ExecuteAsync();
}