bugfix/test fix (#7)

* Add logic for confidence_indicator api usage

* Add google-auth and requests

* Add variable for usps service info

* Remove CSRF middleware

Removing the csrf middleware since by default, when using the Django
Rest Framework (which is used commonly within give, but not for this
service at this time), the usage of views.APIView implies that the view
is exempt from csrf checking. See
https://github.com/encode/django-rest-framework/blob/fd017d00f938c6629d2eeb1b4d81716dff6d006e/rest_framework/views.py

* Read secrets from environment

* Add usps public key for ssl validation

* Remove keyerror on invalid settings

usps/settings.py

@@ -19,8 +19,8 @@
 
 # USPS-specific settings
 if not DEBUG:
-    USPS_SERVICE_INFO = os.environ["USPS_SERVICE_INFO"]
-    USPS_TARGET_AUDIENCE = os.environ["USPS_TARGET_AUDIENCE"]
+    USPS_SERVICE_INFO = os.environ.get("USPS_SERVICE_INFO")
+    USPS_TARGET_AUDIENCE = os.environ.get("USPS_TARGET_AUDIENCE")
 
 # Set production renderer to JSONRenderer instead of the browsable API
 if not DEBUG: