Add links to reference source .NET implementation for Cargo
Add some more notes
Merge pull request #11 from paulrayner/notes

Add some more notes
Add mongoid notes.
Merge pull request #12 from paulrayner/mongoid

Add mongoid notes.
Create failing specs for Delivery.
Start adding methods to Delivery. Tests not passing yet.
Get test passing naively.
Start adding logic to Delivery.
Fix up first Delivery spec. Add code for 2nd spec.
Get compiling.
Fix logic a little for Delivery.
Get 2nd Delivery spec passing.
3rd spec for Delivery.
Get final Delivery spec passing.
Extract method to create fake handling event.
Use fake handling event in all specs.
Get last known location tests passing.
Get last known location specs passing properly.
Get specs passing naively for misdirected Cargo.