Add more CM server tests.
Update MySQL/PostgreSQL dependencies.

Now test against puppetlabs/mysql 2.1.0 and puppetlabs/postgresql
3.2.0.
Update puppetdoc to reflect new requires in cm::server.

Make sure to fully qualify all external classes.
Update README.md to add links to puppetlabs/mysql and
puppetlabs/postgresql.
Revert support for puppetlabs/postgresql 3.x.

It looks like adding puppetlabs/postgresql 3.x on a Puppet Enterprise
3.0 or 3.1 install will break PE.
https://ask.puppetlabs.com/question/4907/will-updating-puppetlabspostgresql-in-puppet-enterprise-3-cause-problems/
Merge branch 'feature/update_deps' into develop