Teal 13 14 acu115241 support mingw

@ryanwilliamson added a mingw implementation specifically for ruby 1.9.3
v2.0.1
was able to use Open3 and did not need to compile an extension, but kept the practice of pre-building a platform specific gem because the Linux implementation uses fork & exec (not possible in Windows).
updated support for mswin binaries, will keep this code at least until right_popen v3.0 appears (if ever) even though we may or may not build mswin gems in future.
made some modules auto-loading but kept the custom delay-loading logic for RightPopen module itself.