Bump version

Bump version for v0.1.3 release

Better detection of interactive stdin

When run from cron, stdin is not a tty so gsheet would always expect
input making it impossible to read data. This change makes it so gsheet
only expects input when stdin is a tty OR if stdin and stdout are both
pipes and there is no data in stdin.

Should fix #7

csv: implement --append

The csv subcommand can now append data to the end of a table found in
range. Fixes #6.

See: https://developers.google.com/sheets/api/reference/rest/v4/spreadsheets.values/append

To append the contents of data.csv to the end of Sheet1, for example:

$ cat data.csv | gsheet --id SHEETS_DOC_ID --range Sheet1 --append

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