Rename class names

data_structures/linked_lists/double_list.rb

@@ -1,4 +1,4 @@
-class DoubleList
+class DoublyLinkedList
   # Initialize your data structure here.
   attr_reader :head, :tail, :size
 
@@ -165,7 +165,7 @@ class Node
   end
 end
 
-obj = DoubleList.new
+obj = DoublyLinkedList.new
 obj.get(1)
 
 obj.add_at_head(2)

data_structures/linked_lists/single_list.rb

@@ -10,7 +10,7 @@ end
 
 # A Class for single linked lists (each element links to the next one, but not to the previous one)
 
-class SingleList
+class SinglyLinkedList
   include Enumerable
   attr_accessor :head
 
@@ -75,7 +75,7 @@ class SingleList
   end
 end
 
-obj = SingleList.new
+obj = SinglyLinkedList.new
 
 obj.insert_head(1)
 obj.insert_head(2)