fix: cards never show up after they were removed once (#174)

* fix: cards never showing up after they were removed once

Bug: If I remove the card of a certain location (eg. New York) and then add it again, it won't show up.
This is due to, the 'hidden' attribute. When I add the location again, the card remains 'hidden'.
I think, removing the DOM element is a clean and expected way to handle this.

* refactor: removing cards

removing the DOM element instead of setting the visibility

public/scripts/app.js

@@ -58,7 +58,7 @@ function addLocation() {
  */
 function removeLocation(evt) {
   const parent = evt.srcElement.parentElement;
-  parent.setAttribute('hidden', true);
+  parent.remove();
   if (weatherApp.selectedLocations[parent.id]) {
     delete weatherApp.selectedLocations[parent.id];
     saveLocationList(weatherApp.selectedLocations);