alternative socket path for postgis

[vchrisb]

For "postgres//..." it is possible to configure an alternative socket path.
This is handled here: https://github.com/joke2k/django-environ/blob/master/environ/environ.py#L405

But this option is not enabled for postgist, making it not possible to configure a non standard socket path.

I guess it should be:
if url.scheme == 'postgres' or url.scheme == 'postgis' and path.startswith('/'):

[sergeyklay]

This is resolved in develop branch. Thank you for the report, and for helping us make django-environ better. And I am sorry about the delay.