Add deprecation warning

WrapExcel::Book.new and WrapExcel::Book.open will be split.
WrapExcel::Book.new will be used create new excel file.

lib/wrap_excel/book.rb

@@ -11,6 +11,10 @@ def open(file, options={ }, &block)
     end
 
     def initialize(file, options={ }, &block)
+      unless caller[1] =~ /book.rb:\d+:in\s+`open'$/
+        warn "DEPRECATION WARNING: WrapExcel::Book.new and WrapExcel::Book.open will be split. If you open existing file, please use WrapExcel::Book.open.(call from #{caller[1]})"
+      end
+
       @options = {
         :read_only => true,
         :displayalerts => false,

spec/book_spec.rb

@@ -54,6 +54,22 @@
       end
     end
 
+    it 'should not output deprecation warning' do
+      capture(:stderr) {
+        book = WrapExcel::Book.open(@simple_file)
+        book.close
+      }.should eq ""
+    end
+
+  end
+
+  describe ".new" do
+    it 'should output deprecation warning' do
+      capture(:stderr) {
+        book = WrapExcel::Book.new(@simple_file)
+        book.close
+      }.should match /DEPRECATION WARNING: WrapExcel::Book.new and WrapExcel::Book.open will be split. If you open existing file, please use WrapExcel::Book.open.\(call from #{File.expand_path(__FILE__)}:#{__LINE__ - 2}.+\)\n/
+    end
   end
 
   describe 'access sheet' do