Add Windows support

Hi.
I've created a patch to add support for windows hosts, aimed to close #49. The basics of the patch are:
- It adds a ruby version of the bash script.
- ~~Creates a new params.pp to store platform specific variables.
  (file mode, owners, paths, names,...)~~
- ~~Refactor to point variable references to params.pp.~~
- Refactor setup.pp to generalize variables according to $::kernel fact.
- Generalizes command execution according to variables in ~~params.pp~~ setup.pp.

I'd like your input/test in this modifications.

The ruby script is a first version trying to match 1-1 the bash structure. Anyway, it needs to be polished and improved as not all the ordering options available in .sh are implemented.