Minor improvements (fixes #20)

- update bstats
- add advancedachievements-achievement full name
- fix 1.8 compatibility
- add placeholder full name

src/main/java/sh/okx/rankup/requirements/requirement/ItemRequirement.java

@@ -37,7 +37,7 @@ public class ItemRequirement extends DeductibleRequirement {
   @Override
   public double getProgress(Player player) {
     Material material = Material.matchMaterial(getSub());
-    return Arrays.stream(player.getInventory().getStorageContents())
+    return Arrays.stream(player.getInventory().getContents())
         .filter(item -> item != null && item.getType() == material)
         .mapToInt(ItemStack::getAmount).sum();
   }

src/main/java/sh/okx/rankup/requirements/requirement/PlaceholderRequirement.java

@@ -49,6 +49,12 @@ public class PlaceholderRequirement extends Requirement {
     throw new IllegalArgumentException("Invalid operation: " + parts[1]);
   }
 
+  @Override
+  public String getFullName() {
+    String[] parts = getValueString().split(" ");
+    return parts[0];
+  }
+
   @Override
   public Requirement clone() {
     return new PlaceholderRequirement(this);

src/main/java/sh/okx/rankup/requirements/requirement/advancedachievements/AdvancedAchievementsAchievementRequirement.java

@@ -21,6 +21,11 @@ public class AdvancedAchievementsAchievementRequirement extends Requirement {
     return api.hasPlayerReceivedAchievement(player.getUniqueId(), getValueString());
   }
 
+  @Override
+  public String getFullName() {
+    return super.getFullName() + "#" + getValueString();
+  }
+
   @Override
   public Requirement clone() {
     return new AdvancedAchievementsAchievementRequirement(this);