Fix wrong config.py location (#16)

* Move config.py to inside the package

* Import config.py as .config on client.py

Author: Jonatas Baldin

yoti_python_sdk/client.py

@@ -11,7 +11,7 @@
 from past.builtins import basestring
 
 import yoti_python_sdk
-from config import SDK_IDENTIFIER
+from .config import SDK_IDENTIFIER
 from yoti_python_sdk.activity_details import ActivityDetails
 from yoti_python_sdk.crypto import Crypto
 from yoti_python_sdk.protobuf.v1 import protobuf