Specify template during createdb

[kmatzen]

I ran the existing install_postgres.sh script.

createdb: database creation failed: ERROR:  new encoding (UTF8) is incompatible with the encoding of the template database (SQL_ASCII)
HINT:  Use the same encoding as in the template database, or use template0 as template.

Recommended update:
Change

createdb -p $DB_PORT --owner=$DB_USER --encoding=UTF8 $DB_NAME

to

createdb -p $DB_PORT --owner=$DB_USER --encoding=UTF8 --template=template0 $DB_NAME

I can follow up with a PR if you're interested.