Cp test

This is a simple test that checks if the docker cp command works.  It copies a single file from a container and makes sure it was copied successfully.  I chose '/bin/cp' as the default file to copy as it is small and I figure it would be on most docker linux images.  This could be changed as the testers need or easily expanded to take in lists of files down the road.

Its only external requirement is the 'mktemp' command which is provided in coreutils.  I could do this pythonicly with the tempfile library, but I decided to go with this as it figures out the systems tmp directory out for me.  Let me know if you'd like me to change that.