s/zsh/Zsh/g

github:
fixed #1
Add slide about rebasing branches

github:
fixed #4
Expand on data integrity

github:
fixed #3
Work in feedback by Joey Hess, other clarifications
Get rid of legacy procedure
More details for git-annex working, partially hidden
Update date
Add version held on 2013-03-10 as videotaped talk
Merge branch 'source'
Merge branch 'slides'