Update Apache commons-io to version 2.4.

Version 2.4 is able to clean up circular symlinks.

See https://github.com/gocd/gocd/issues/360#issuecomment-50403790

Signed-off-by: Aravind SV <arvind.sv@gmail.com>
Merge pull request #676 from pivotal-cf-experimental/recursive-symlink-clean-working-directory

Update Apache commons-io to version 2.4.