Fixed incorrect man path with ruby installation path

[Bug #15359][ruby-core:90164]

lib/bundler/cli.rb

@@ -123,6 +123,8 @@ module Bundler
       end
 
       man_path  = File.expand_path("../../../man", __FILE__)
+      # man files are located under the share directory with the default gems of bundler
+      man_path = File.expand_path("../../../../../share/man/man1", __FILE__) unless File.directory?(man_path)
       man_pages = Hash[Dir.glob(File.join(man_path, "*")).grep(/.*\.\d*\Z/).collect do |f|
         [File.basename(f, ".*"), f]
       end]