Update 'lambda test' tail option default value

[clifff]

Calling test through Thor's invoke method has unexpected behavior when passing a :tail option.

Before this change, regardless of what options are passed to invoke, options[:tail] comes out as false. With this change, there is no key for :tail in options if nothing is passed in the options hash, and if :tail is passed, it comes through as expected.

[rlister]

I have no idea why this is the case, but thanks for figuring it out!