Switch to module-relative import syntax.

Now that the python scripts are all in a "redo" python module, we can
use the "new style" (ahem) package-relative imports.  This appeases
pylint, plus avoids confusion in case more than one package has
similarly-named modules.

redo/env.py

@@ -1,5 +1,5 @@
 import os, sys
-from atoi import atoi
+from .atoi import atoi
 
 is_toplevel = False