Add an i18n solution

[mturley]

Text in the UI is defined directly in React components as English-language strings.

If the intention is ever to add multi-language support, we should start using something like https://github.com/formatjs/react-intl (or investigate what others are using) to wrap strings in a function call that could return translated forms of the strings in the future. Even if we can't add the actual translations until much later, it would help to establish the usage of this kind of library so it is easier to add languages in the future.

[eriknelson]

@jwmatthews is this a required feature?