Master

• Validates scan status transitions (https://github.com/rackerlabs/scantron/issues/204)
• Allows paused scans to be cancelled without having to go through "cancel" state (https://github.com/rackerlabs/scantron/issues/206)
• Bumped Master Django version to 2.2.13 for https://github.com/rackerlabs/scantron/pull/211

Agent

• Bumped agent.py to version 1.01 - prettified json scan object for easier reading in logs