I am suing Heroku dev plan for creating database using PostgreSQL. Database is created in Heroku. After running heroku pg:info command
$ heroku
It took a little digging, but I was able to use it by running this command:
heroku run /app/php/bin/php /app/www/artisan migrate
So the lesson I learned was this: prefix all remote artisan commands with heroku run /app/php/bin/php /app/www/artisan
heroku run /app/php/bin/php /app/www/artisan