Correct ordering for expected / got
Unindent 'nrml' helper method

Trying to replace the recursive normalize with a local one... exposing
the node-node function ought to be useful.
Simplify shortcut / left path
Push normalization into the insert function, and remove some recursion

Instead of renormalizing the trie each time, which grows increasingly
wasteful as the tree enlarges, we should normalize locally as we make
changes.

I suspect this is still not minimal, but at least it's *local* --
the work on each insert will be proportional to the depth of the tree,
not the entire size.
Rename nrml -> normalize

It's the only one left, so it gets the good name.
Factor out normalization call

Turns out this was used on every branch, so might as well factor it out
entirely...