Add 'dis' component

This commit adds a new 'dis' component to the distillery that serves a
list of all known instances for the moment.

env/server.go

@@ -0,0 +1,31 @@
+package env
+
+import (
+	"io"
+	"net/http"
+)
+
+// Server represents a server for this distillery
+type Server struct {
+	dis *Distillery
+}
+
+func (dis *Distillery) Server() *Server {
+	return &Server{
+		dis: dis,
+	}
+}
+
+func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	instances, err := s.dis.AllInstances()
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		io.WriteString(w, "Something went wrong")
+		return
+	}
+
+	w.WriteHeader(http.StatusOK)
+	for _, instance := range instances {
+		io.WriteString(w, instance.Slug+"\n")
+	}
+}