Add internationalization

[LarrySheen]

Can we have a i18n version/sub version with JSON file compatible? considering users are from different country.
I will commit a Traditional Chinese/Simplified Chinese for translation if there's a customizable JSON file.

[Endebert]

Currently, all strings are hardcoded in english, no efforts towards internationalization have been made so far.

Nevertheless, I think this is a great idea. I've worked with vue-i18n professionally already, and would welcome its integration to this project.

The following steps would be required to add internationalization to this app:

• move all hardcoded strings into a i18n locale JSON file
• replace hardcoded strings with vue-i18n lookup
• load correct locale based on browser locale or user setting
• add ability to let user select language
• let community add/edit locales in some way
  • we could just store the locales in the repository as a start, however I would prefer to use some kind of service that facilitates our efforts (mostly to highlight missing translations)
  • I'm only familiar with Phrase, which doesn't seem to have a solution for a community based approach

I'll welcome any contributions to get this implemented.