Remove she-bang and x bit from scuba/__main__.py

This can already no longer be directly executed as a script, so there's
no point in either of these. It can however, be executed as a module,
e.g. $ python -m scuba, so leave the 'if __name__'... at the end of the
file.

scuba/__main__.py

@@ -1,5 +1,3 @@
-#!/usr/bin/env python2
-
 # SCUBA - Simple Container-Utilizing Build Architecture
 # (C) 2015 Jonathon Reinhart
 # https://github.com/JonathonReinhart/scuba