Put wordlist into a Trie data structure

[dmuth]

This is a continuation of #2, which I am splitting into two separate issues.

It was suggested in that issue that I store the words in a Trie, which would be more space efficient. While that seems straightforward, and I can figure out how to create the Trie, it's not 100% clear to me how I would do traversal in a manner that takes less space than the words themselves, assuming each node in the Trie holds 1 character.

I may need to go do some Google searches for how PKzip worked, as it uses a Trie to compress text, IIRC.