// PUT api/Tags/5
        public HttpResponseMessage PutTag(int id, Tag tag)
        {
            if (!ModelState.IsValid)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            if (id != tag.Id)
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }

            db.Entry(tag).State = EntityState.Modified;

            try
            {
                db.SaveChanges();
            }
            catch (DbUpdateConcurrencyException ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.NotFound, ex);
            }

            return Request.CreateResponse(HttpStatusCode.OK);
        }
        // POST api/Tags
        public HttpResponseMessage PostTag(Tag tag)
        {
            if (ModelState.IsValid)
            {
                db.Tags.Add(tag);
                db.SaveChanges();

                HttpResponseMessage response = Request.CreateResponse(HttpStatusCode.Created, tag);
                response.Headers.Location = new Uri(Url.Link("DefaultApi", new { id = tag.Id }));
                return response;
            }
            else
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }
        }