[abdul7056]

Repro: run autoflake --recursive --in-place proj on a tree where proj/link.py is a symlink to a Python file outside proj/. The target file is rewritten, so a checked-out repository can point the in-place edit at any Python file the user can write.
Cause: find_files passes every file symlink reported by os.walk() on to fix_file, which reads and writes through the link. Directory symlinks were already not followed, so file symlinks were the only way out of the tree.
Fix: skip, before the file is opened, any symlink in the recursive walk whose resolved target is not under the resolved walk root. Symlinks that stay within the tree and files named explicitly on the command line are unchanged. Added a find_files regression test that fails on the old code.