Add csv import

[xet7]

Moved to here from phildini#27

From @paulproteus

CSV from what? From logtacts? If so, I suggest not bothering and just doing
JSON, but up to you.​

From @phildini

I basically want to accept as many upload formats as possible, to make it real easy for people to get their stuff into the app.

When importing from CSV, should be able to add a tag to all imported contacts.

So I want to be able to import CSV from Google and Outlook, and I think I want this to happen browser-side. http://papaparse.com/ seems to be a good way to accomplish this, plus some API endpoints.