Try to fix markdown.

free-programming-books-de.md

@@ -3,8 +3,8 @@
 * [iOS](#ios)
 * [Java](#java)
 * [Python](#python)
-* [Ruby on Rails](#rubyonrails)
-* [Visual Basic](#visualbasic)
+* [Ruby on Rails](#ruby on rails)
+* [Visual Basic](#visual basic)
 
 ###Android