Add input_array.pop!

For pry-de's ,- command.

lib/pry/history_array.rb

@@ -89,6 +89,11 @@ class Pry
       ((@count - size)...@count).map { |n| @hash[n] }
     end
 
+    def pop!
+      @hash.delete @count - 1
+      @count -= 1
+    end
+
     def inspect
       "#<#{self.class} size=#{size} first=#{@count - size} max_size=#{max_size}>"
     end

test/test_history_array.rb

@@ -59,4 +59,9 @@ describe Pry::HistoryArray do
     12.times { |n| @array << n }
     @array.entries.compact.size.should == 10
   end
+
+  it 'should pop!' do
+    @populated.pop!
+    @populated.to_a.should == [1, 2, 3]
+  end
 end