ansible.utils._git_repo_info() now supports branch names with slashes

##### Issue Type:

Bugfix Pull Request

##### Ansible Version:

```
ansible 1.9 (devel a0ff0f8198) last updated 2014/12/11 12:48:59 (GMT +900)
  lib/ansible/modules/core: (devel 467ad65f73) last updated 2014/12/11 12:49:52 (GMT +900)
  lib/ansible/modules/extras: (detached HEAD b8071a8d5e) last updated 2014/12/11 12:49:14 (GMT +900)
  v2/ansible/modules/core: (detached HEAD cb69744bce) last updated 2014/10/14 16:46:09 (GMT +900)
  v2/ansible/modules/extras: (detached HEAD 8a4f07eecd) last updated 2014/10/14 16:46:21 (GMT +900)
  configured module search path = None
```

##### Environment:

OSX 10.9

##### Summary:

If your branch name contains a `/`, the branch name is not shown properly.

##### Steps To Reproduce:

`git checkout -b test/git-repo-info-branch`

##### Expected Results:

```
$ ansible --version
ansible 1.9 (fixes/git-repo-info-branch 51073de72f) last updated 2014/12/11 12:54:45 (GMT +900)
...
```

##### Actual Results:

```
$ ansible --version
ansible 1.9 (detached HEAD git-repo-i) last updated 2014/12/11 12:57:46 (GMT +900)
...
```