Merge trunk revision: 39327

* lib/rubygems/commands/update_command.rb:  Create the installer after
  options are processed.  [ruby-trunk - Bug #7779]
* test/rubygems/test_gem_commands_update_command.rb:  Test for the
  above.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_0_0@39344 b2dd03c8-39d4-4d8f-98ff-823fe69b080e