.Then() and .And() extension methods

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This is a wish list sort of thing, but it would be really awesome if we there 
were .And and .Then methods on Tweeners.

.And on a Tweener would take and return create another Tweener after setting 
the Delay to the current Tweener's delay.

.Then on a Tweener would take and return another Tweener with the Delay set to 
the current Tweener's delay + its duration.

These could also be implemented more efficiently via Sequences, but sequences 
are a bit more verbose to build, and usually, I prefer the conciseness over the 
speed.

I can't quite implement these using extension methods currently, because 
there's no method to get the delay from a Tweener.

Thanks!

Original issue reported on code.google.com by thematth...@gmail.com on 7 Sep 2014 at 7:59