Translations support

[srallen]

#40 adds a MVP for Spanish translations for WD and the MapViewer. Long term, though, we should look into using react-intl which will handle all localization needs. Grommet uses react-intl under the hood and we'll get some localization for free for the icons, Timestamp, and Notification components: https://github.com/grommet/grommet/tree/master/src/js/messages
They currently do not support Spanish, but I imagine the team would accept a pull request from us.