Enhanced edit feature 

Here are some enhancements that I think will be useful. 

1. Multiple edits via regular expression on host 

```bash
vagrant@precise32:/vagrant$ python storm/ list
listing entries:
    google-01 -> vagrant@www1.google.com:22 
	[custom options] identityfile=/home/vagrant/.ssh/test

    google-02 -> vagrant@google.com:22 
	[custom options] identityfile=/home/vagrant/.ssh/test

vagrant@precise32:/vagrant$ python storm/ edit google-0[1-2] --o user=test
success  "google-0[1-2]" updated successfully.
```

Multiple edit modifies config of hosts who match regular expression
```bash
vagrant@precise32:/vagrant$ python storm/ list
listing entries:
    google-01 -> test@www1.google.com:22 
	[custom options] identityfile=/home/vagrant/.ssh/test

    google-02 -> test@google.com:22 
	[custom options] identityfile=/home/vagrant/.ssh/test
```

2. Modified usage of edit; id_file and connection_uri are now optional. If they are not passed their values will not change. Saves some typing. 

```bash
usage: storm edit [-h] [--connection_uri CONNECTION_URI] [--id_file ID_FILE]
                  [--o O]
                  name

positional arguments:
  name

optional arguments:
  -h, --help            show this help message and exit
  --connection_uri CONNECTION_URI
  --id_file ID_FILE
  --o O
```