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.
content for airco, security in datacenters

Filled some content for review
Update sysadmin_tools.rst

adding byobu usage
line length, description

lines wrapped at 80 chars, added short description about Byobu and why
you should use it
A few minor things before getting into ssh stuff.

* Add mention that one's environment can dictate the tools one uses.

* Small blurb about iTerm 2.

* Fix 'previous' typo; should've been 'precious'.
Added screen usage
interstitial ssh examples
adding initial content to hardware
Point people at github's git docs for now

We'll want to actually cover git and github in the curriculum, for sure.
For now, pointing people to the docs Github have already written should
provide at least some useful info. I've also pointed people at the IRC
channel if github's docs are insufficient.
Fix the tyop, thanks Mike
Merge pull request #91 from apeiron/topic/apeiron/git-github-docs

Point people at github's git docs for now
updates links for some redirects and remote vs local
whitespace removals
Merge branch 'master' of https://github.com/FlorianHeigl/curriculum into FlorianHeigl-master
Fixing warnings for list indentation
whitespace removals
datacenters 201: typos
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
Try to explain a littl about crisis management.

Just an incomplete first draft. Needs more detail.