Add the exclude so that the cloning is smaller

.lfsconfig

+[lfs]
+  fetchexclude="*"

README.md

+# Frama-C Website #
+
+This is the working space for the Frama-C website. It uses Jekill, but you don't
+have to install anything, since everything is generated by the continuous integration.
+
+# For contributing #
+
+Get Git LFS from the `git-lfs` package or directly from:
+```
+curl -s https://packagecloud.io/install/repositories/github/git-lfs/script.deb.sh | sudo bash
+sudo aptitude install git-lfs
+```
+
+Get the repository normaly:
+```
+git clone git@git.frama-c.com:frama-c/frama-c.frama-c.com
+```
+
+The bigfiles of the website (*.pdf, *.tar.gz) are not directly in the git
+repository, only a text file is present.
+
+You can download locally one file:
+
+```
+git lfs pull -X "" -I foo.pdf
+```
+
+Or all pdf:
+
+```
+git lfs pull -X "" -I "*.pdf"
+```
+
+
+If you want to edit the website before the release, for updating informations,
+for releasing your plugin, I strongly encourage you to do so. As usual you can use a
+branch `feature/...` and a merge-request to `master`.
+
+If you want to add a bigfile you have nothing to do. `git push` will
+send the needed files.