Add random language generator

Languages are taken from data/languages.json and generate a random
language and region combination. Default all combinations are considered
but optionally a base language can be provided to limit the choices.
Script to fetch language information

The fetch_languages.js script will fetch language information from the
unicode consortium repository and output it. This script can be used to
update the data/languages.json file.

The depencies for the script are set as devDependencies in package.json.
Documentation tweaks
Merge pull request #1 from mattijs/language

Language generator