Update Dockerfile, docker-compose, and package.json; add versioning script and styles for version display

Fix #21

public/index.html

@@ -61,6 +61,7 @@
             </div>
             <button class="btn waves-effect waves-light" type="submit">Spara uppgift</button>
             <p id="responseMessage"></p>
+            <p id="version"><!-- VERSION_PLACEHOLDER --></p>
         </form>
     </div>