Move gemspec files to top of lib directory.

  They have version.rb files with same directory.
  But version.rb have been removed at ruby/ruby#3375
  There is no reason to locate under the library name of directory.

Author: hsbt

weakref.gemspec

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