Rails 4 upgrade! Tests are running but not passing. Changes:
* update a lot of gems
* update application.rb for rails 4
* added config.eager_load to the environment files
* updated conditions hashes on has_many relations
* took out modernizr (maybe we don't need it?)
Add Rails 4 schema and fix a migration to remove index better

In Rails 4, renaming a table or column changes the index name. So the from-scratch
migration path was broken, since it deleted an index by the (now different) name.

Deleting it by referencing the associated columns seems to work all the time, so let's just do that.
Clean up Guardfile
Remove faulty sass include directive
Remove whiny_nils
Get rid of rails 4 deprecation warnings:
* .scoped has become .all
* implicit table joins need .references
* scopes need ugly lambdas
* get rid of whiny nils. I hated them.
* secret_token is now secret_key_base
Fix specs for EventsController

* Make stuff attr_accessible on Event
Fix rsvps_controller specs by fixing accessible attributes on rsvp and rsvp_session.