Updated version info to include submodule information

`ansible --version` etc. now include information about submodules

```
ansible 1.8 (submodule_ansible_version ffee9a8fe0) last updated 2014/09/28 11:03:14 (GMT +1000)
  lib/ansible/modules/core: (ec2_snapshot_remove 3a77c31ecb) last updated 2014/09/27 18:23:31 (GMT +1000)
  lib/ansible/modules/extras: (detached HEAD 110250d344) last updated 2014/09/27 14:33:42 (GMT +1000)
```

Also improved handling of detached HEAD when printing out version
information.