Fix some typos

Signed-off-by: Thomas Ackermann <th.acker@arcor.de>
Fix commit reference
Merge pull request #146 from tritemio/master

Fix commit reference
Merge pull request #143 from tacker66/fix_some_typos

Fix some typos
Contributing.md
Translation and figure notes -> contributing.md
License for print edition
asciidoc != markdown
Merge pull request #142 from progit/contributors-guide

Contributor's guide