v1.3.0

Simulation schema is upgraded to v5.1 to support the following new features (a big thanks to @ns3777k):

• Adding delay to a specific response

• Serving response body from a file

The binary size is up a few MBs after switching to go mod since v1.2.0, so this release strip off the debugger info to squeeze it down a little bit while we come up with a plan for hoverfly to lose some weight.