It doesn't look very good for "native" apps to overscroll when scrolling. Would be nice to have a BrowserWindow option to disable overscroll

![untitled12](https://cloud.githubusercontent.com/assets/170270/15033357/fc36e32e-1293-11e6-8cdc-6c17b0f504dd.gif)
## 
- Electron version: 0.37.8
- Operating system: OS X 10.11.4

atom/browser/web_contents_preferences.cc
if (web_preferences.GetBoolean(options::kExperimentalFeatures, &b) && b)
    command_line->AppendSwitch(
        ::switches::kEnableExperimentalWebPlatformFeatures);
  if (web_preferences.GetBoolean(options::kExperimentalCanvasFeatures, &b) && b)
    command_line->AppendSwitch(::switches::kEnableExperimentalCanvasFeatures);
  
  bool node_integration = true;
  web_preferences.GetBoolean(options::kNodeIntegration, &node_integration);
  command_line->AppendSwitchASCII(switches::kNodeIntegration,
                                  node_integration ? "true" : "false");
  
  base::FilePath::StringType preload;
  if (web_preferences.GetString(options::kPreloadScript, &preload)) {
    if (base::FilePath(preload).IsAbsolute())
      command_line->AppendSwitchNative(switches::kPreloadScript, preload);
    else
      LOG(ERROR) << "preload script must have absolute path.";
  } else if (web_preferences.GetString(options::kPreloadURL, &preload)) {
    
    base::FilePath preload_path;
    if (net::FileURLToFilePath(GURL(preload), &preload_path))
      command_line->AppendSwitchPath(switches::kPreloadScript, preload_path);
    else
      LOG(ERROR) << "preload url must be file:// protocol.";
  }
  
  std::string color;
  if (web_preferences.GetString(options::kBackgroundColor, &color))
    command_line->AppendSwitchASCII(switches::kBackgroundColor, color);