TNT Minecarts now destroy rails and underlying blocks

The Bug

In previous versions TNT Minecarts were unable to destroy rails and their underlaying blocks (MC-7879) which was intended because of (https://twitter.com/Dinnerbone/status/291237104976019456). Now they do explode rails and underlying blocks.

Reproduce

• Turn on the Minecart Experiment
• Get some rails and a TNT Minecart
• Activate the TNT Minecart

Observed Result

The rails exploded

Expected Result

They wouldn't explode