Add .editorconfig
Drop libpciaccess dependency

Using libDRM's method, we can count the ordinal number of CUDA available devices.
And libpciaccess is not needed any more in libgdev.
Support non-root gdev with render nodes

Close #30

Leveraging newly added DRM *render nodes* architecture,
DRM can restrict the priviledges to render nodes with file based permission.
So, by opening splitted `/dev/dri/renderD%d` device file, if the user have
permission to this file, the user can execute GPGPU applications without root
permission.
Currently, typically, `video` group is allowed to access this device file.
So by adding the user to `video` group, the non-root user can use gdev.

[1]: http://dvdhrm.wordpress.com/2013/05/29/drm-render-and-modeset-nodes/
Update README.cmake.md
Update README.gdev.md
Update README.nouveau.md
Update README.nvrm.md
Update README.pscnv.md
compiler: added PTX compilers using LLVM and Open64(nvopencc)