Local development: support 127.0.0.1 too

So, after I set up the local env, I visited 127.0.0.1:8080. Now, I know the README states localhost but localhost translates to 127.0.0.1 too so if it's not too much trouble both should be supported.

shakes fist at Google Cloud

This should be easy, but every time I touch the relevant file I also cause a bug due to unforeseen issues with Google Cloud:

hstspreload.org/hstsserver.go

Lines 23 to 26 in 0e96795

    
           func isLocalhost(hostport string) bool { 
        
           	host, _, err := net.SplitHostPort(hostport) 
        
           	return err == nil && host == "localhost" 
        
           }

@lgarron: something else I wonder after setting things up locally. In README.md you mention:

cd $GOPATH/src/github.com/chromium/hstspreload.org

I personally just had to cd to the repository and do make serve. Also $GOPATH isn't available on my Windows VM, $GOROOT was set though by the installer.

	func isLocalhost(hostport string) bool {
	host, _, err := net.SplitHostPort(hostport)
	return err == nil && host == "localhost"
	}