Google Sheets support

[LouisDeconinck]

It would be nice to import data from Google Sheets automatically.

I followed these examples:
https://github.com/andymeneely/squib/wiki/Automatic-Google-Sheets-CSV-Export and #164

But none of them worked, I get the following error:

deck.rb:5:in `initialize': Invalid argument @ rb_sysopen - GOOGLESHEETSLINK (Errno::EINVAL)
        from deck.rb:5:in `open'
        from deck.rb:5:in `<main>'

[andymeneely]

See #164, also #350