Ensure ruby 1.8.7 support for nimsoft_dirscan provider

The nimsoft_dirscan nimsoft provider did not work on ruby 1.8.7 because
"GB"[0] does not return the first character but the first byte. Make
sure that the code works on both ruby 1.8.7 and ruby>=1.9

see also
http://stackoverflow.com/questions/2730854/ruby-how-to-get-the-first-character-of-a-string