Bump unicorn from 5.0.1 to 5.4.0
Bump unicorn from 5.0.1 to 5.4.0

Bumps [unicorn](https://bogomips.org/unicorn/) from 5.0.1 to 5.4.0.
FundingCircle/shipment_tracker,FundingCircle/shipment_tracker,FundingCircle/shipment_tracker,FundingCircle/shipment_tracker