Add support for setting alias when creatign instance. (#140)

* Add support for setting alias when creatign instance.

The POST to create a instance now provides an `alias` field which
then can be used to access the instance services through the following
URL:

`http://<alias>-<short_session>-<port>.<tld>`

When creating a session you can now send an `alias`

* Remove unnecessary function

* Add alias support for DNS resolution

handlers/new_instance.go

@@ -13,7 +13,7 @@ func NewInstance(rw http.ResponseWriter, req *http.Request) {
 	vars := mux.Vars(req)
 	sessionId := vars["sessionId"]
 
-	body := struct{ ImageName string }{}
+	body := struct{ ImageName, Alias string }{}
 
 	json.NewDecoder(req.Body).Decode(&body)
 
@@ -26,7 +26,7 @@ func NewInstance(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 
-	i, err := services.NewInstance(s, body.ImageName)
+	i, err := services.NewInstance(s, body.ImageName, body.Alias)
 	if err != nil {
 		log.Println(err)
 		rw.WriteHeader(http.StatusInternalServerError)