Revert "Update README.md"

This reverts commit 4c43eb49e64b78b272f2c75dfdd4664a7991c0be.
Add German translation

Add the German translation for Purity III
Fix Back-To-Top Issue

Is the page height less than the screen height the Back-To-Top-Button
looks pretty awful. This commit solve this.
Merge pull request #7 from danielang/master

Add the German Translation