Refactored Eventbrite API integration

The Eventbrite API events integration now operates based on a configured
email address, which prevents events created by other users from
appearing on the events page. The API configuration variables (key,
email, cache expiration) were moved to utilize Rails.configuration, and
the API cache module was refactored to both allow use of the new
configuration options and remove extraneous caching calls. Finally, the
environment-specific configurations were given some default values for
the Eventbrite API integration.
Fixed broken logo asset
Simplified Events index view
Merge pull request #5 from YoPro/feature/bem-secure-eventbrite-integration

Feature/bem secure eventbrite integration