Add setting for turning on/off link tracking. Doesn't yet do anything though
Rename open_tracking_domain to custom_tracking_domain to reflect more general use
using: btree added to schema.rb i'm thinking by rails 4.0.0.rc1
New filter that splits out text and html parts of email for separate processing
Beginnings of LinkTrackingFilter
New model Link
New model DeliveryLink
Roughed out implementation of link tracking
Add roughly formatted link to example test email
Add first pass at link tracking redirect code
Use the correct host and protocol for the link
Respect app setting for whether to apply link tracking
Switch on link tracking