Refactor Trie __init__, reduce complexity

[bact]

This PR will close #381

[pep8speaks]

Hello @bact! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2020-05-04 18:41:29 UTC

[coveralls]

Coverage increased (+0.01%) to 91.099% when pulling 3faa0cc on refactor-trie into b329aa8 on dev.

[korakot]

I prefer to leave Trie.Node.add(..) the same.

You could add another Trie.add_word(..) instead.

[bact]

I prefer to leave Trie.Node.add(..) the same.

You could add another Trie.add_word(..) instead.

Maybe better that way. So we can add new word after the trie has been created, if needed.

[bact]

Changed accordingly.

I keep the method name add() for brevity.
Also add len() to Trie.