Added a usage placeholder section.
Added a 'Requirements' section and 'Other Requirements' subsection.
Renamed section.
Added explanation and links to the things the module sets up.
Added server requirements section text.
Added general requirements section text.
Added sections for server and client usage.
Added basic server usage section.
Moved some usage stuff out of the requirements section and instead added some example Puppet code that shows how to set up a Postgres database.
Added commas to the ends of the last parameters in the list.
Added a basic client usage example.
Added distro links.
Added a note about how the ::server and ::client classes can be used separately.
Merge branch 'feature/documentation' into develop