add comprehensive gitattributes file with sane export-ignore and auto lf
add comprehensive gitattributes file with sane export-ignore and auto lf

prolixtechnikos/LiipImagineBundle,liip/LiipImagineBundle,prolixtechnikos/LiipImagineBundle,robfrawley/LiipImagineBundle,liip/LiipImagineBundle,prolixtechnikos/LiipImagineBundle,robfrawley/LiipImagineBundle