Update .travis.yml, Gemfile, Rakefile, and CONTRIBUTING.md
Add json gem

The puppet_facts gem implicitly depends on the json gem.
On Ruby 1.8.7, json is not built in. On Puppet 2.7, it is
not explicitly pulled in by the hiera gem. So we add it
here explicitly.
Merge pull request #544 from cmurphy/master

Update .travis.yml, Gemfile, Rakefile, and CONTRIBUTING.md
(MODULES-1383) Add restart parameter

This commit adds a restart parameter to both
postgresql::server and postgresql::server::config_entry