Update documentation to use generators

[tsroten]

The current documentation assumes that the output format is a list, but CLI Helpers now returns generators. We should update the quick start and the API documentation.

[aashraybhandar1]

Can I be assigned this issue

[amjith]

@aashraybhandar1 Go forth and send a PR. We won't start working on it.

Github only allows people with commit access to the repo to have assignments. So I can't officially assign it to you but I can assure you that we're not actively working on it.

[aashraybhandar1]

The result of the various adapters is a generator so the change should be made for the format_output option ? @tsroten @amjith

[meeuw]

I think a good start would be to verify the documentation in:
https://github.com/dbcli/cli_helpers/blob/master/docs/source/quickstart.rst

The examples return list_iterator objects instead of lists, I think this needs to be updated to "\n".join(...)