How to use Postgres 9.6.1 on circleci 14.04 image

circle.yml

# Other settings have been omitted, the below changes are relevant
machine:
  pre:
    - sudo service postgresql stop
    - sudo apt-get purge -y postgresql*
    - sudo apt-get update
    - sudo apt-get install postgresql
    - sudo service postgresql start
    - sudo su - postgres -c "echo \"create user ubuntu with password 'ubuntu';\" | psql"
    - sudo su - postgres -c "echo \"alter user ubuntu with superuser;\" | psql"
    - sudo su - postgres -c "echo \"create database ubuntu;\" | psql"
database:
  override:
    - mv config/database.ci.yml config/database.yml
    - bundle exec rake db:create db:structure:load --trace

database.ci.yml

# config/database.ci.yml
test:
  adapter:  postgresql
  database: circle_ruby_test
  username: ubuntu
  password: ubuntu
  encoding: unicode