patchx

Hi, @luislavena

I change exerb-mingw into a gem;

and test it on ruby 2.0.0p481, update some outdated testcase/example.

Can you check example/vruby and example/rubytk ? how to packaged tcl file to exe ?

@windwiny do you have `devkit` gem installed? Because `require "devkit"` on RubyInstaller will load RubyInstaller's DevKit, unless of course `devkit` gem is installed.

Too bad the gem developers decided to use that name :cry: