v1.7.3

This is a patch release that mostly incorporates test & build system updates, as well as fixing a rare cause of panics.

CHANGELOG

• Update stale.yml (#494) @elithrar
• Improve CORS Method Middleware (#477) @fharding1
• Delete ISSUE_TEMPLATE.md (#492) @elithrar
• Use subtests for middleware tests (#478) @fharding1
• Delete .travis.yml (#490) @elithrar
• Fix nil panic in authentication middleware example (#489) @fharding1
• [WIP] Create CircleCI config (#484) @elithrar