Feature/Addition Host domain

[dmuriel]

This PR adds new functionality for Buffalo, by using the Host function from Gorilla/Mux, buffalo can now restrict the handlers and render those that only match the specified host. This is very useful if you have multiple portals in the same application and/or want to use the same path for different portals.

...

func HomeApp(c buffalo.Context) error {
	return c.Render(http.StatusOK, r.String("OK APP"))
}

func HomeLMS(c buffalo.Context) error {
	return c.Render(http.StatusOK, r.String("OK LMS"))
}

func New() *buffalo.App {
	bapp := buffalo.New(buffalo.Options{
		Env:         envy.Get("GO_ENV", "development"),
		SessionName: "_application_session",
	})

        app := bapp.Host("app.domain.com")
        app.GET("/dashboard", HomeApp) // This will render the dashboard for the Application

        lms := bapp.Host("lms.domain.com")
        lms.GET("/dashboard", HomeLMS) // This will render the dashboard for the LMS

	return bapp
}

...

When testing, you need to specify the exact path, including the host, otherwise it will return a 404:

func (as ActionSuite) Test_App_Dashboard() {
    // This one will not throw a 404
    res := as.HTML("http://app.domain.com/dashboard/").Get()
    as.Equal(http.StatusOK, res.Code)
    as.Contains(res.Body.String(), "OK APP")
}

func (as ActionSuite) Test_LMS_Dashboard() {
    // This one will throw a 404
    res := as.HTML("http://cms.domain.com/dashboard/").Get()
    as.Equal(http.StatusOK, res.Code)
    as.Contains(res.Body.String(), "OK LMS")
}

[paganotoni]

Thanks for this one @dmuriel! Love it.

[saurori]

I created a PR for adding this to the docs: gobuffalo/docs#605