make sure slashes are forward for windows machines from gettext module

I was getting an error after install that templates could not read nonetype on paster serve.  Traced it to splitting the files with forward slash only.
Depending on the core contributors' preference, making sure there are forward slashes could be done a number of ways.  I just did the first approach that popped in my head.  os.name == 'nt' might be a more elegant solution.