Improved classification of subdivision/unit

[missinglink]

branched from stopword-classification, requires https://github.com/pelias/parser/pull/179 be merged first.

This PR is an attempt at solving https://github.com/pelias/parser/issues/178 with minimal changes.

However, it seems to solve a longstanding issue which was more widespread, namely having a space between HouseNumber and UnitNumber:

node bin/cli.js 10 A Main Street

# before
(0.98) ➜ [ { housenumber: '10' }, { street: 'A Main Street' } ]

# after
(0.86) ➜ [ { housenumber: '10 A' }, { street: 'Main Street' } ]

I'm going to have a think about this before merging, it feels 'too easy', I'm sure it comes with some pitfalls.

Closes https://github.com/pelias/parser/issues/178