federated identities not passed into aws-exports properly

[adrianhall]

When we have Cognito, Facebook, or Amazon federated identities, the Amplify library requires a federated object:

const federated = {
    google_client_id: '',
    facebook_app_id: '',
    amazon_client_id: ''
};

return (
    <Authenticator federated={federated}>
)

Update the google and facebook (and add amazon) to the federated object, rather than being listed directly.

[adrianhall]

Fixed with #34