Windows ANSI color support - experimental

The idea is to pipe the `elixir` output to another app (`bin\wac.exe` by ) that intercepts ANSI sequences and converts them into colors. If the `wac` app is not found, we simply use the default output...

![image](https://f.cloud.github.com/assets/155977/864014/a6455a54-f617-11e2-89c8-18a85c56e497.png)

To test/use it, run `make compile_windows`, and make sure you have GCC installed.