git cheat-sheet: cite github instead of sf.net

Signed-off-by: Yvan Volochine <yvan.volochine@gmail.com>
tutorials: update Getting started link to doc.sccode.org

Signed-off-by: Yvan Volochine <yvan.volochine@gmail.com>
git cheat-sheet: comments format in code examples should be consistent

Signed-off-by: Yvan Volochine <yvan.volochine@gmail.com>
Merge pull request #22 from gusano/topic/nomore_sf.net

Topic/nomore sf.net