Update for Riak CS 1.5

- Update Riak cookbook for 2.4.14 (riak 1.4.10)
- Replace yum/apt repos with packagecloud repos
- Remove Ubuntu 13.04 support (EOL)
- Add Ubuntu 14.04 support
- Update AWS AMI to 2014.03.2
The equivalent AMI (PV EBS-Backed 64-bit) for 2014.03.2 in `us-east-1` is `ami-7c807d14`.