Make sclack installable from pip in a more universal fashion

[SteveMcGrath]

Moved the app.py and config.json files within the sclack package and updated the setup.py to use the refactored entrypoint to start the script.

This should make the sclack application installable from pip. and usable via the commandline as “sclack”

[marsam]

you also need to update tests/test_api.py

diff --git c/tests/test_api.py i/tests/test_api.py
index 952088a..a57272f 100644
--- c/tests/test_api.py
+++ i/tests/test_api.py
@@ -1,5 +1,5 @@
 from sclack.quick_switcher import remove_diacritic
-from app import ask_for_token
+from sclack.app import ask_for_token
 
 from slackclient import SlackClient