Add support for "application/x-yaml" (getkin#421)

Schema customization plug-point (getkin#411)

feature: Add more discriminator error messages and return specific er… (

getkin#394)

* feature: Add more discriminator error messages and return specific error when possible

* feature: Always show more specific error message

* test: Add schema oneOf tests

* clean: Add missing word

Fix handling recursive refs (getkin#403)

Accept multipart/form-data's part without Content-Type (getkin#399)

fix: Allow encoded path parameters with slashes (getkin#400)

Add support for embedded struct pointers (getkin#396)

Support reference cycles (getkin#393)

Add missing yaml tags in marshaling openapi2.T (getkin#391)

reproduce and fix issue getkin#382 (getkin#383)