Affix Postgres to version 9.1.

Addresses #362.

roles/mailserver/tasks/dovecot.yml

     - dovecot-managesieved
     - dovecot-pgsql
     - dovecot-pop3d
-    - postgresql-9.3
+    - postgresql-9.1
   when: ansible_distribution_release == 'trusty'
 
 - name: Create vmail group

roles/mailserver/tasks/postfix.yml

     - sasl2-bin
   when: ansible_distribution_release != 'trusty'
 
-- name: Install Postfix 9.3 and related packages for Ubuntu Trusty
+- name: Install Postfix 9.1 and related packages for Ubuntu Trusty
   apt: pkg={{ item }} state=installed
   with_items:
     - libsasl2-modules
     - postfix
     - postfix-pcre
     - postfix-pgsql
-    - postgresql-9.3
+    - postgresql-9.1
     - postgrey
     - python-psycopg2
     - sasl2-bin

roles/owncloud/tasks/owncloud.yml

     - libapache2-mod-php5
     - php-apc
     - python-psycopg2
-    - postgresql-9.3
+    - postgresql-9.1
 
 - name: Set postgres password
   command: sudo -u {{ db_admin_username }} psql -d {{ db_admin_username }} -c "ALTER USER postgres with  password '{{ db_admin_password }}';"