Remove needless `:env => :win`
Remove needless `:env => :win`

`:env => :win` means that the example doesn't run on Windows. The
example should work on Windows. So `:env => :win` should not be
specified.

Reported by Masahiro Nakagawa. Thanks!!!

tarcieri/cool.io,cosmo0920/cool.io,nurse/cool.io,nurse/cool.io,tarcieri/cool.io,cosmo0920/cool.io,tarcieri/cool.io