Local development: support 127.0.0.1 too

[XhmikosR]

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.

[lgarron]

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"
	}

[XhmikosR]

@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.