I've been trying to get this to work by following the answers in these questions:

• 

• The uninstaller will do its thing and then prompt you with this:

• At this point you'll want to follow the steps provided in this PREVIOUS StackOverflow ANSWER - steps 3 through 6 of @user1181328's answer. I'll list them here for convenience:

3. Remove the PostgreSQL and data folders. The Wizard will notify you that these were not removed.
   sudo rm -rf /Library/PostgreSQL

4. Remove the ini file:
   sudo rm /etc/postgres-reg.ini

5. Remove the PostgreSQL user:

   • using System Preferences -> Users & Groups.
   • Unlock the settings panel by clicking on the padlock and entering your password.
   • Select the PostgreSQL user and click on the minus button.

6. Restore your shared memory settings:
   sudo rm /etc/sysctl.conf

That should be all! The uninstall wizard would have removed all icons and start-up applications files so you don't have to worry about those.