Allow bashate to be called as a module

Adops official way of calling a module as a script.
Now user can do `python -m bashate ...` which can prove
to be useful when scripts cannot be installed or
when debugging is desired, or use of specific
python interpreter.

Change-Id: I7b3085df3e9f5874cf22470fec15c1b0532c846d
Signed-off-by: Sorin Sbarnea <ssbarnea@redhat.com>

bashate/__main__.py

@@ -0,0 +1,5 @@
+from bashate import main
+import sys
+
+if __name__ == "__main__":
+    sys.exit(main())