Fix PR #357

Turns out that comments are associated with a specific AST node in
python, and are not AST nodes on their own. Therefore, "continue" after
detecting the shebang comment in fact causes the future import to be
placed after the first AST node, which might be anything.

Author: flaviut

src/libfuturize/fixer_util.py

@@ -243,7 +243,6 @@ def future_import(feature, node):
         # Is it a shebang or encoding line?
         if is_shebang_comment(node) or is_encoding_comment(node):
             shebang_encoding_idx = idx
-            continue
         if is_docstring(node):
             # skip over docstring
             continue