adds support for customizable apt sources
Merge pull request #69 from engineyard-cookbooks/ppa_support

adds support for customizable apt sources
add contribution from @alenia to the README
Add ability to use an apt keyserver for pg installation
Merge pull request #71 from engineyard-cookbooks/apt-keyserver

Add ability to use an apt keyserver for pg installation
add contributions from @alenia and @Randommood
adds basic kitchen tests for postgresql cookbook
add initial Test Kitchen integration tests:

* replace initial `bats` setup with `serverspec`
  framework
* add ubuntu-(12|13).04, debian-(6|7) platforms 
* add `default` suite
* add `server` suite with a basic `default_server`
  smoke test
* run with vagrant locally and ec2 on Travis CI
cleanup supporting bundler configuration
simplify `.kitchen.yml` for now:

* only use vagrant locally, skip on CI for now
  until a better long-term solution is available