Update readme with "diaper_dev" as db name (#1048)
Update readme with "diaper_dev" as db name (#1048)

The development database name in database.yml is "diaper_dev",
but the README identifies it as "diaper_development". This commit
updates the README to match the value in database.yml.
rubyforgood/diaper,rubyforgood/diaper,rubyforgood/diaper,rubyforgood/diaper