When running auth command, don't overwrite an existing auth.json file

[ashanan]

Ran the auth command in the same directory I'd previously set up an auth.json file for twitter-to-sqlite and it was completely overwritten. Not the biggest issue, but still unexpected. Ideally, for me, the keys would just be added to the existing file, but getting a warning and a chance to back out would be a good solution as well.

[simonw]

Agreed, that would be a much better implementation.

[simonw]

That was clearly the intention from the description of this issue:

• Store authentication information as "pocket_access_token" etc #4

[ashanan]

Thanks!