Support CONFLICT response for Google Cloud's API

If the status code for a call to the Google Cloud's API is 409 (CONFLICT), and
the code of the error is 'alreadyExists', consider the resource as already
existing and create the correct error.

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
The default ttl for Google Cloud's API is 0.

The default can't be `None' since we're calling `int' on the value of ttl.

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
The 3rd argument for GoogleDNSConnection is secure, not scope.

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Reformat the code for pep8

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Update changes.

Closes #378