Add updates=file src=file argument to command

This patch add src=file updates=file arguments to command module.
It will run command only if `updates` is older than `src` like `makefile` does.

```yaml
- command: /do_compile_script src=/tmp/source updates=/bin/binary

- name: test iptables
  command: /sbin/iptables-restore /etc/sysconfig/newiptables
                   src=/etc/sysconfig/newiptables
                   updates=/etc/sysconfig/iptables
  notify:
     - save iptables
```