Don't drop database in load.sh

We want to be able to use this script to get the latest data into the app in
production with zero downtime. To do that, we need to import the data without
dropping the entire database, which is what the `robust` rake tasks do.
Merge pull request #75 from alphagov/dont_drop_database_in_load_sh

Don't drop database in load.sh
Merge commit 'd4f48e6c89d376b9efa0838902a7302f7e50eb62' into HEAD