PDF presentations shouldn't be in Git

All of the PDFs from this years OVScon were recently added to the Git repo. However, this makes cloning the repo extremely slow as all of these PDFs must be checked out. Could we upload these to a proper, SaaS presentation hosting site instead? I use SpeakerDeck personally, as it lets you use your GitHub credentials, but I'm not sure if they support organizations (you don't want to be sharing credentials for a single account). I've emailed to ask them, but in the interim SlideShare do appear to offer such a feature.

检查 commit b654854813 中添加的 PDF，并比较 SpeakerDeck 和 SlideShare 对组织的支持情况。确定托管方案，将 OVScon 演示文稿移出 Git 仓库，并验证演示文稿仍可访问，同时在克隆时不再下载这些文件。