Include instruction for AMI 2014.03

Include instructions to install Docker from Amazon's Software Repository on new AMI 2014.03 (Release Candidate)

Docker-DCO-1.1-Signed-off-by: Sebastien Stormacq <sebastien.stormacq@gmail.com> (github: sebsto)
Merge pull request #4715 from sebsto/patch-1

Include instruction for AMI 2014.03