update migrations to devise 2.0 schema style

Updated the the migrations (including db/schema.rb) to match the devise 2.0 schema style found at https://github.com/plataformatec/devise/wiki/How-To%3a-Upgrade-to-Devise-2.0-migration-schema-style

I am suggesting this change since the https://github.com/pglombardo/PasswordPusher/blob/master/Gemfile.lock#L73 is using a devise 2.0+ version and was not working for a brand new setup unless these changes were made.