Fixed filename for Open3::VERSION

lib/open3/open3.gemspec

@@ -2,7 +2,7 @@
 
 name = File.basename(__FILE__, ".gemspec")
 version = ["lib", Array.new(name.count("-")+1, "..").join("/")].find do |dir|
-  break File.foreach(File.join(__dir__, dir, "#{name.tr('-', '/')}.rb")) do |line|
+  break File.foreach(File.join(__dir__, dir, "#{name.tr('-', '/')}/version.rb")) do |line|
     /^\s*VERSION\s*=\s*"(.*)"/ =~ line and break $1
   end rescue nil
 end