This PR intends to move the gh-pages away from the branch and into the docs/ folder. This makes it easier to update individual pages and allows us keep a clear track on the changes.

This PR takes care of the following things:

• Commit a69dc22 puts the newest html files into the docs/ folder.
• Commit f50c15b changes the n_procs paramter in all notebooks to 8
• Commit 8dd6f19 updates update_pages.sh, which converts notebooks and moves them into the docs/ folder. It still shouldn't be used fully automated, but at least there's no ugly rm -rf command anymore.
• Commit 708d0fa adds my .gitconfig tocreate_dockerfile.sh, so that we don't get the git Warning with datalad anymore.
• Commit 2bacd52 moves the reveal.js folder from the notebook folder into the docs/ folder.
• Commit da63228 tries to prevent the long "red box warnings" in the notebooks, that occure if %matplotlib inline% is run before nilearn.plotting`.