```ruby
include_attribute 'travis_build_environment'

default['postgresql']['default_version']     = '9.1'
default['postgresql']['alternate_versions']  = %w(9.2 9.3 9.4 9.5)

default['postgresql']['enabled']             = true    # is default instance started on machine boot?

default['postgresql']['port']                = 5432
default['postgresql']['ssl']                 = true
default['postgresql']['max_connections']     = 255
default['postgresql']['fsync']               = false   # disabled for CI purpose
default['postgresql']['full_page_writes']    = false   # disabled for CI purpose
default['postgresql']['client_min_messages'] = 'error' # suppress warning output from build clients

default['postgresql']['data_on_ramfs']       = true    # enabled for CI purpose

if node['postgresql']['data_on_ramfs']
  default['postgresql']['data_dir']          = "#{node['travis_build_environment']['ramfs_dir']}/postgresql"
else
  default['postgresql']['data_dir']          = '/var/lib/postgresql'
end

default['postgresql']['contrib_modules']     = true    # enabled to install additional modules, like `hstore`
# (see full list at http://www.postgresql.org/docs/devel/static/contrib.html)

default['postgresql']['client_packages']     = %w(postgresql-client libpq-dev)

default['postgresql']['postgis_version']     = '2.2'

default['postgresql']['superusers']          = [node['travis_build_environment']['user'], 'rails']
```

Add 9.6 to postgresql alternate versions
user
```ruby
include_attribute 'travis_build_environment'

default['postgresql']['default_version']     = '9.3'
default['postgresql']['alternate_versions']  = %w(9.1 9.2 9.4 9.5 9.6)

default['postgresql']['enabled']             = true    # is default instance started on machine boot?

default['postgresql']['port']                = 5432
default['postgresql']['ssl']                 = true
default['postgresql']['max_connections']     = 255
default['postgresql']['fsync']               = false   # disabled for CI purpose
default['postgresql']['full_page_writes']    = false   # disabled for CI purpose
default['postgresql']['client_min_messages'] = 'error' # suppress warning output from build clients

default['postgresql']['data_on_ramfs']       = true    # enabled for CI purpose

if node['postgresql']['data_on_ramfs']
  default['postgresql']['data_dir']          = "#{node['travis_build_environment']['ramfs_dir']}/postgresql"
else
  default['postgresql']['data_dir']          = '/var/lib/postgresql'
end

default['postgresql']['contrib_modules']     = true    # enabled to install additional modules, like `hstore`
# (see full list at http://www.postgresql.org/docs/devel/static/contrib.html)

default['postgresql']['client_packages']     = %w(postgresql-client libpq-dev)

default['postgresql']['postgis_version']     = '2.2'

default['postgresql']['superusers']          = [node['travis_build_environment']['user'], 'rails']
```
assistant