cli: add --lang to pick the greeting language

tests: cover config parsing edge cases

Add --format=json for scripting

Add --count to repeat the greeting

Implements: https://todo.hut.md/~reviewer/hello-hut/2

tests: add a phrasebook fixture for snapshot tests

The fixture is generated: 50 given names and 40 family names, each
in plain and shouted form.

Add --time-of-day greetings

Add --shout to print the greeting in capitals

Use str.upper() so that accented names keep their accents.

tests: add unit tests for greet()