Session class fix for target server address containing dot notation (.)

If the target url contained an address with dot notation, the domain was being stripped off when using the Session class.
```
s = Session('windows-host.example.com', auth=('john.smith', 'secret'))
``` 
would cause the url to be
```
http://windows-host:5985/wsman
```
Which would cause the run_cmd method to fail. Changed the Session._build_url re.match to account for dot notation. Also created a test for this scenario.