Make it works on ArchLinux

Hi,
glad to find your  repo and it has help me a lot in my own cuda project. Thank you!

There is an official package for cuda in ArchLinux
but 

    ./configure --with-cuda=/opt/cuda

doesn't work. So i made another makefile for it, by edited the cuda template sample makefile.

    renderer-cuda-archlinux/Makefile

BTW, there is another package for lib3ds in AUR. Therefore the lib3ds folder in your repo is never used, the codes about lib3ds including have been changing either.

    renderer-cuda-archlinux/*.cpp *.h *.cu

and I've changed the readme file.

Best Wishes.