client.accountsDF() error with single account

[danielgrzenda]

A dictionary is returned from client.accounts(). When calling client.accountsDF() with a single account this throws an error, because json_normalize expects a group of records.

[dahifi]

@danielgrzenda this is fixed in current master.

I'm not going to close it because there's no test coverage. Should just be as simple as adding

            m.return_value.json.return_value = [{'test': 1}]
            tdclient.accountsDF()

to the end of testclient.test_accounts.