Try to run Pacproxy with Node.js

On Windows environment, it is difficult to run javascript runtimes which like therubyracer.
So, I want to add Node.js runtime. I need to do followings.

- [x] autodetect to run with Node.js
- [x] enable to run with Node.js
- [x] improve speed with Node.js
- [x] refactor
- [x] enable to run Node.js on <del>both Windows and</del> *nix.
- [x] add enough tests
- [x] build npm installation process
- [x] build CI processes for both therubyracer and Node.js
- [x] add READNE.md description