Docker setup for drupal 7 and 8

instructions

First install docker and docker-compose tools.

1. just put drupal 7 code in d7 subdirectory and drupal 8 code in d8 subdirectory.
2. then run docker-compose build
3. then run docker-compose up
4. D7 should be accessible on http://localhost:8251 and D8 on http://localhost:8250