command-line interface

Hi

Thanks for the work on pywinrm. I'm using it in several projects.

This pull request contains a WinRM CLI using pywinrm. I need it for doing quick WinRM interactions. In general it works, except that multiline cmd commands doesn't work:

```
$ ./winrm -p password Administrator@10.0.0.10 <<\EOF
echo 1
echo 2
EOF
1
```

Do you have any idea why? 

*Note*: executing multiline scripts using powershell work:
```
$ ./winrm -t ps -p password Administrator@10.0.0.10 <<\EOF
echo 1
echo 2
EOF
1
2
```

Other working examples are in the code.

kind regards,
Jakob