Add #to_ary to Diff::LCS::Change and Diff::LCS::ContextChange

It would be quite handy if you could write as follows:

```ruby
Diff::LCS.sdiff(a, b).each do |action, (old_position, old_element), (new_position, new_element)|
  case action
  when '!'
    # replace
  when '-'
    # delete
  when '+'
    # insert
  end
end
```

lib/diff/lcs/change.rb

@@ -41,6 +41,8 @@ def to_a
     [ @action, @position, @element ]
   end
 
+  alias to_ary to_a
+
   def self.from_a(arr)
     arr = arr.flatten(1)
     case arr.size
@@ -132,6 +134,8 @@ def to_a
     ]
   end
 
+  alias to_ary to_a
+
   def inspect(*args)
     to_a.inspect
   end

spec/change_spec.rb

@@ -62,4 +62,28 @@
     it { should_not be_finished_a }
     it { should     be_finished_b }
   end
+
+  describe "as array" do
+    it "should be converted" do
+      action, position, element = described_class.new('!', 0, 'element')
+      expect(action).to eq '!'
+      expect(position).to eq 0
+      expect(element).to eq 'element'
+    end
+  end
+end
+
+describe Diff::LCS::ContextChange do
+  describe "as array" do
+    it "should be converted" do
+      action, (old_position, old_element), (new_position, new_element) =
+        described_class.new('!', 1, 'old_element', 2, 'new_element')
+
+      expect(action).to eq '!'
+      expect(old_position).to eq 1
+      expect(old_element).to eq 'old_element'
+      expect(new_position).to eq 2
+      expect(new_element).to eq 'new_element'
+    end
+  end
 end