Added group_create function to postgres module

Allows for creating a postgres "group". Groups and Users are both Roles
in postgres. Groups simply cannot login while Users can.
Added option to user and group create in postgres module

Can now provide a string of groups (comma seperated) to place the new
user/group in.
Added function to update a group in postgres

Added ability to provide groups for a user update and function to update
a group
Added function to remove a group
Merge pull request #3287 from shadowfax-chc/postgres-group

Added some support for postgres groups to the postgres module
Defer imports to a later stage so Jinja2 does not become a build dependency. Fixes #3293.
Merge pull request #3294 from s0undt3ch/issues/3293

Defer imports to a later stage so Jinja2 does not become a build dependency. Fixes #3293.
Jinja2 is no longer a build dependency. Fixes #3293.
Merge pull request #3295 from s0undt3ch/issues/3293

Jinja2 is no longer a build dependency. Fixes #3293.
Use `salt.utils.fopen` within `salt.utils`? Nope! How did it even work?!