renamed --screw-ie to --screw-ie8, documented it in README.md, indicated it doesn't break IE9+

README.md

@@ -54,6 +54,9 @@ The available options are:
                        --source-map.                                      [string]
     --in-source-map    Input source map, useful if you're compressing JS that was
                        generated from some other original code.
+    --screw-ie8        Pass this flag if you don't care about full compliance with
+                       Internet Explorer 6-8 quirks (by default UglifyJS will try
+                       to be IE-proof.
     -p, --prefix       Skip prefix for original filenames that appear in source
                        maps. For example -p 3 will drop 3 directories from file
                        names and ensure they are relative paths.