Fixes some capitalization

src/main/java/net/knarcraft/bookswithoutborders/handler/BookshelfHandler.java

@@ -27,8 +27,8 @@ import java.util.logging.Level;
 public class BookshelfHandler {
 
     private static final File bookshelfFile = new File(BooksWithoutBorders.getInstance().getDataFolder(),
-            "bookShelves.yml");
-    private Set<Bookshelf> bookShelves;
+            "bookshelves.yml");
+    private Set<Bookshelf> bookshelves;
     private Map<Location, Bookshelf> locationLookup;
 
     /**
@@ -48,7 +48,7 @@ public class BookshelfHandler {
      * @param bookshelf <p>The bookshelf to register</p>
      */
     public void registerBookshelf(@NotNull Bookshelf bookshelf) {
-        this.bookShelves.add(bookshelf);
+        this.bookshelves.add(bookshelf);
         this.locationLookup.put(bookshelf.getLocation(), bookshelf);
     }
 
@@ -59,14 +59,14 @@ public class BookshelfHandler {
      */
     public void unregisterBookshelf(@NotNull Bookshelf bookshelf) {
         this.locationLookup.remove(bookshelf.getLocation());
-        this.bookShelves.remove(bookshelf);
+        this.bookshelves.remove(bookshelf);
     }
 
     /**
      * Loads all stored bookshelves
      */
     public void load() {
-        this.bookShelves = new HashSet<>();
+        this.bookshelves = new HashSet<>();
         this.locationLookup = new HashMap<>();
 
         YamlConfiguration configuration = YamlConfiguration.loadConfiguration(bookshelfFile);
@@ -113,7 +113,7 @@ public class BookshelfHandler {
         try {
             YamlConfiguration configuration = new YamlConfiguration();
             ConfigurationSection bookshelfSection = configuration.createSection("bookshelves");
-            for (Bookshelf bookshelf : bookShelves) {
+            for (Bookshelf bookshelf : bookshelves) {
                 saveBookshelf(bookshelfSection, bookshelf);
             }
             configuration.save(bookshelfFile);