adds HistoryArray#to_h and spec

lib/pry/history_array.rb

@@ -89,6 +89,11 @@ class Pry
       ((@count - size)...@count).map { |n| @hash[n] }
     end
 
+    # Returns [Hash] copy of the internal @hash history
+    def to_h
+      Marshal.load( Marshal.dump(@hash) )
+    end
+
     def pop!
       @hash.delete @count - 1
       @count -= 1

spec/history_array_spec.rb

@@ -64,4 +64,8 @@ describe Pry::HistoryArray do
     @populated.pop!
     @populated.to_a.should == [1, 2, 3]
   end
+
+  it 'should return an indexed hash' do
+    @populated.to_h[0].should == @populated[0]
+  end
 end