Fixed rake file calls by using system() instead of exec()

# We now have YOLO

Showhow in all that git resolve conflict shuffle, the rake file wasn't updated. This is the updated one.

Now instead of doing these following:

- rake db:drop
- rake db:create
- rake db:migrate
- rake db:seed

just run

- rake db:yolo

@jsum528, @ballauriena, @juandefelix, I feel I've done very little so far. I'd like to actually write something useful.