Enh tail

[tacaswell]

Only look at the second commit.

This is mostly for discussion. As with #38 this is a useful function, but not sure it is useful enough / has a 'correct' enough API to be worth shipping with the package and they can instead (continue to) live as examples in the documentation (as with https://docs.python.org/3.5/library/itertools.html#itertools-recipes)

[danielballan]

I lean toward preferring this as a documented example.

[WeatherGod]

ditto. Plus, I am not so keen on the idea of having to specify a dictionary to be the tail. If you have the dictionary, then why not just chain the cycler and a cycle of that dictionary together? If I want my cycler to have a long tail, then I would likely want its last element to be the tail item.