Add Continuous Deployment to our Travis system
As a development group, we need out automated CI system to find problems in the deployment packages when they are introduced so that we can avoid a 'package building log-jam' at release time.
To implement this:
Use the Travis 'build stages' feature to trigger package builds only if the 'regular' build succeeds.
Use Docker to provide the build environments for CentOS 6 and 7. 
Use the native Ubuntu 14 OS for debian packages.
Name the packages using build numbers, git commit hashes (first 7 digits is generally considered good enough). Also, look at `git rev-parse --short=7 --verify HEAD` which will give you a seven digit hash if it's unique, or add more digits as needed. 
Push these to an AWS bucket. We can use the current bucket used for the test results, but that clutters things up. Note that the Travis builds have a special 'deployment' part for this and we're using it already.
These packages are not all to be released - we might build the packages for release by hand still - so we can assume that we sign and get them to the web site 'manually.'
Do this for both libdap and bes