How to remove Postgres from my installation?

The simplest way to do this is to open a terminal and type:

sudo apt-get --purge remove postgresql

This will also prompt you to remove that software that depends on Postgres, which in this case it appears you would like to do.
I do not personally run 9.10 or Postgres, so it is possible that Postgres installs itself in several parts. In that case, a simple:

dpkg -l | grep postgres

Will get you the list of those packages that Postgres installed. Then, just use the same "apt-get --purge remove ...." command but instead of just postgresql, type each package name, separated by spaces, like:

sudo apt-get --purge remove postgresql postgresql-doc postgresql-common

This is dependent on the list of packages installed, of course.

Steps that worked for me on Ubuntu 8.04.2 to remove postgres 8.3

1. List All Postgres related packages

   dpkg -l | grep postgres
   
   ii  postgresql                            8.3.17-0ubuntu0.8.04.1           object-relational SQL database (latest versi
   ii  postgresql-8.3                        8.3.9-0ubuntu8.04                object-relational SQL database, version 8.3
   ii  postgresql-client                     8.3.9-0ubuntu8.04                front-end programs for PostgreSQL (latest ve
   ii  postgresql-client-8.3                 8.3.9-0ubuntu8.04                front-end programs for PostgreSQL 8.3
   ii  postgresql-client-common              87ubuntu2                        manager for multiple PostgreSQL client versi
   ii  postgresql-common                     87ubuntu2                        PostgreSQL database-cluster manager
   ii  postgresql-contrib                    8.3.9-0ubuntu8.04                additional facilities for PostgreSQL (latest
   ii  postgresql-contrib-8.3                8.3.9-0ubuntu8.04                additional facilities for PostgreSQL
   

2. Remove all above listed

   sudo apt-get --purge remove postgresql postgresql-8.3  postgresql-client  postgresql-client-8.3 postgresql-client-common postgresql-common  postgresql-contrib postgresql-contrib-8.3
   

3. Remove the following folders

   sudo rm -rf /var/lib/postgresql/
   sudo rm -rf /var/log/postgresql/
   sudo rm -rf /etc/postgresql/
   

4. Remove the postgres user:

   sudo deluser postgres
   

One command to completely remove postgresql in terminal is sudo apt-get --purge remove postgresql\*. Please note that this command will remove postgresql and all it's compenents.