relativize modernize internal imports

Author: graingert

modernize/__main__.py

@@ -2,7 +2,7 @@
 
 import sys
 
-from modernize.main import main
+from .main import main
 
 if __name__ == "__main__":
     sys.exit(main())

modernize/main.py

@@ -15,8 +15,8 @@
 from fissix import refactor
 from fissix.main import StdoutRefactoringTool, warn
 
-from modernize import __version__
-from modernize.fixes import fissix_fix_names, opt_in_fix_names, six_fix_names
+from . import __version__
+from .fixes import fissix_fix_names, opt_in_fix_names, six_fix_names
 
 usage = (
     __doc__