feature: Add support for culture/language like fr-FR

[hongymagic]

Changes dependency from much outdated numeral.js to numbro.js, and add optional culture property.

<NumberInput {...props} culture="fr-FR" />

• Formats numbers like the French would (1 000 000 and 1,35)
• Sensible defaults have been left as en-US as it's numbro default (no en-AU…)
• Supports all the cultures supported by the foretagsplatsen/numbro library

DEMO

https://cdn.rawgit.com/hongymagic/react-number-input/feature/numbro/demos/demo0/index.html

TODO

• Culture tests
• Loading all the cultures are expensive and heavy; may need to rework that (demos0/demo0/all.js sitting at 60kb)

But everything seems to work ok now.

Fixed #12, #14