Add support for os specific feature detection

Similar to how we have ruby feature detection this ports the `windows?` method from core and adds a method for detecting windows file paths (a sort of follow up to #108), idea would be to replace the usage of `world.windows?` with this and refactor #108 
I'd support that, WDYT @myronmarston? Something like:

```Ruby
def uses_standard_path?
  File::ALT_SEPERATOR == nil
end
```

Which we could then use to conditionally define the method in #108 ?