Clarify cifs volume sharing

I wanted to mention that using --volumes-from how you get the shared container available in other containers. 

Docker-DCO-1.1-Signed-off-by: Michael Neale michael.neale@gmail.com (github: michaelneale)
Merge pull request #421 from michaelneale/master

Clarify cifs volume sharing docs
Add util-linux for nsenter
Add -no-pad not to pad output
version bump