updated cloud install example per Olivier's comments, added better command examples
updates per @thaJeztah comments
fixed links per @theJeztah comments, renamed cloud.md to overview.md for better URL name
updates per @moxiegirl comments, added alias for renamed file, modified links, changed a title
fixed link errors
Signed-off-by: Victoria Bialas <victoria.bialas@docker.com>
