Example doesn't work due to problem loading hll extension

The log does indicate one needs to add `shared_preload_libraries = 'hll'` to `$PGDATA/postgresql.conf`, so I did try that through adding a `COPY` to `Dockerfile.postgres`, and made sure my script ran before the SQL script (prefixing the shell script with `00` and SQL script with `01`), but the same error still occurred.

```
Attaching to example_postgres_1, example_nemea_1
postgres_1 | The files belonging to this database system will be owned by user "postgres".
postgres_1 | This user must also own the server process.
postgres_1 |
postgres_1 | The database cluster will be initialized with locale "en_US.utf8".
postgres_1 | The default database encoding has accordingly been set to "UTF8".
postgres_1 | The default text search configuration will be set to "english".
postgres_1 |
postgres_1 | Data page checksums are disabled.
postgres_1 |
postgres_1 | fixing permissions on existing directory /var/lib/postgresql/data ... ok
postgres_1 | creating subdirectories ... ok
postgres_1 | selecting default max_connections ... 100
postgres_1 | selecting default shared_buffers ... 128MB
postgres_1 | selecting default timezone ... Etc/UTC
postgres_1 | selecting dynamic shared memory implementation ... posix
postgres_1 | creating configuration files ... ok
postgres_1 | running bootstrap script ... ok
postgres_1 | performing post-bootstrap initialization ... ok
postgres_1 | syncing data to disk ... ok
postgres_1 |
postgres_1 | Success. You can now start the database server using:
postgres_1 |
postgres_1 | pg_ctl -D /var/lib/postgresql/data -l logfile start
postgres_1 |
postgres_1 |
postgres_1 | WARNING: enabling "trust" authentication for local connections
postgres_1 | You can change this by editing pg_hba.conf or using the option -A, or
postgres_1 | --auth-local and --auth-host, the next time you run initdb.
postgres_1 | waiting for server to start....2019-11-19 05:17:15.453 UTC [46] LOG: listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
postgres_1 | 2019-11-19 05:17:15.470 UTC [47] LOG: database system was shut down at 2019-11-19 05:17:15 UTC
postgres_1 | 2019-11-19 05:17:15.476 UTC [46] LOG: database system is ready to accept connections
postgres_1 | done
postgres_1 | server started
postgres_1 | CREATE DATABASE
postgres_1 |
postgres_1 |
postgres_1 | /usr/local/bin/docker-entrypoint.sh: running /docker-entrypoint-initdb.d/initdb-hll.sql
postgres_1 | 2019-11-19 05:17:15.913 UTC [71] ERROR: HLL can only be loaded via shared_preload_libraries
postgres_1 | 2019-11-19 05:17:15.913 UTC [71] HINT: Add hll to shared_preload_libraries configuration variable in postgresql.conf
postgres_1 | 2019-11-19 05:17:15.913 UTC [71] STATEMENT: CREATE EXTENSION IF NOT EXISTS hll;
postgres_1 | psql:/docker-entrypoint-initdb.d/initdb-hll.sql:1: ERROR: HLL can only be loaded via shared_preload_libraries
postgres_1 | HINT: Add hll to shared_preload_libraries configuration variable in postgresql.conf
example_postgres_1 exited with code 3
nemea_1 | tcp-connect: connection failed;
nemea_1 | host not found
nemea_1 | address: postgres
nemea_1 | port number: 5432
nemea_1 | system error: Name or service not known; gai_err=-2
nemea_1 | context...:
nemea_1 | /usr/share/racket/pkgs/db-lib/db/private/postgresql/main.rkt:13:0: postgresql-connect25
nemea_1 | /usr/share/racket/collects/racket/contract/private/arrow-val-first.rkt:430:3
nemea_1 | /usr/share/racket/pkgs/db-lib/db/private/generic/connect-util.rkt:331:25: send-arg636
nemea_1 | .../more-scheme.rkt:261:28
nemea_1 | /usr/share/racket/pkgs/db-lib/db/private/generic/connect-util.rkt:38:19: proc
nemea_1 | /usr/share/racket/pkgs/db-lib/db/private/generic/connect-util.rkt:23:7
example_nemea_1 exited with code 1
```