Tell people not to be the BOFH.

This is a start to the "how not to be a sysadmin" section. I've tried to
achieve some balance between useful guidance and preaching.
Merge branch 'master' into topic/apeiron/what-sysadmin-is-not

Conflicts:
	sysadmin_101.rst
Merge pull request #93 from apeiron/topic/apeiron/what-sysadmin-is-not

Elaborate a bit on what sysadmin is not