Library cleanup.

It's time, I think, to revist this library and make it something to be proud of.
I made some curious decisions in my previos work--largely to explore using
proper--which I would not now make.

This commit does some simple cleanup, removing old, busted tests and leaves the
field open. The next bit of work will be to make this more sound.

Signed-off-by: Brian L. Troutwine <brian@troutwine.us>
Put the library on a firm footing.

The previous implementation had a few defects and was overly complicated. This,
to the best of my deduction, is a correct implementation of a TST. Of note,
perhaps, is the use of zipper strings in partial_matches/3 to effeciently allow
adaptation of the pattern string.

Signed-off-by: Brian L. Troutwine <brian@troutwine.us>
Update README.md.

The readme was in need of a fair bit of updating from it's bare-bones original
text. I've included an example and some background information on this
data-structure.

Signed-off-by: Brian L. Troutwine <brian@troutwine.us>