Standardize shebang and coding declaration

Standardizes shebang and coding declarations.

Coding matches what's used by install tools such as pip(x).

Removes a few init files that were not needed.

bdfr/exceptions.py

@@ -1,4 +1,5 @@
-#!/usr/bin/env
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
 
 
 class BulkDownloaderException(Exception):