According to 3af53522, TLJH is in beta state by now. This commit
replaces the other occurrences in the documentation to make it
consistent. Also syncs other paragraphs from index.rst to README.rst,
see 5374f5ea.
World-Readable seem to be a surprising default for many people,
especially in teaching context. Switch to a more reasonable rwxr-x---
We have to issue a chmod, as changing at creation time would require
changin /etc/adduser.conf DIR_MODE=0760 (or whatever), but that seem
unwise.
We do not set the exact permission in case the DIR_MODE is more
restrictive.
Closing #158
