User and port options are overwritten in update command 

This is a patch to the update command where if the user/port are different from the defaults and are not passed, they are overwritten. 

For example: 

```bash
vagrant@precise32:/vagrant$ python storm search google-01
Listing results for google-01:
    google-01 -> vagrant@google.com:24

vagrant@precise32:/vagrant$ python storm update google-01 --o user=ops
success  "google-01" updated successfully.

vagrant@precise32:/vagrant$ python storm search google-01
Listing results for google-01:
    google-01 -> ops@google.com:22 #port is overwritten 
```

I have also written a test for this and placed this in a separate file. Because of it, I thought it necessary to put all tests in a separate folder. This can only be good for https://github.com/emre/storm/issues/53. I am keen to help out on that too.