platform name conflicts with SmartThings plugin in the homebridge-legacy-plugins package
HomeBridge fails at start when homebridge-legacy-plugins is installed with homebridge-smartthings, and the config stanza in the homebridge-smartthings README.md is used as the basis for configuration. No stanza remained in my config.json for the legacy plugin. 

Both plugins will consume the stanza for platform "SmartThings," though so HomeBridge startup fails. 

The solution is just a small change in config that should be reflected in the instructions. Doing this will not hurt even if you don't have homebridge-legacy-plugins installed. 

Instead of

```
{
    "platform": "SmartThings",
```

preface it with the plugin name to disambiguate the namespace:

```
{
    "platform": "homebridge-smartthings.SmartThings",
```

and you're good! No changes needed to either plugin package. 
