Add recipe for iss-mode

iss-mode is a major mode for editing InnoSetup installation script files (http://www.jrsoftware.org/isinfo.php) - InnoSetup is a tool for generating windows installer packages (setup.exe).

I am not the original author, the original author is Stefan (http://www.xsteve.at/prg/emacs/iss-mode.el), all i did was import his iss-mode.el in a github repo on my account.

I have not contacted Stefan.