Fixes sign up page

The rails4 upgrade broke the sign-up, we need to add the additional
attributes to the devise_parameter_sanitizer

 Fixes #303
in the AddEventIdAtCreationToLinks migration, handle the case of links that don't yet have any events
actually save the link
truncate log messages to 2048 characters
Merge pull request #304 from dsander/sign-up-fix

Fixes sign up page
add Link, Event classes to migration and use find_each
Merge pull request #306 from cantino/truncate_agent_log_messages

truncate log messages to 2048 characters
Merge pull request #305 from albertsun/safer-add-event-id-at-creation-to-links-migration

Small fix for the AddEventIdAtCreationToLinks migration
update to work with newer dotenv; you can pull your production database with: cap sync:db:down
Merge pull request #307 from cantino/fix_capistrano_db_sync

Update capistrano/sync to work with newer dotenv