Add `required` to `Parameter`

0.5.1

Expose Parameter.Location's required property on the Parameter struct

Numerous Additions

Added support for Example Object and with it examples on Components Object and Media Type Object.

Rounded off test coverage of Media Type Object.

Added a number of other small things.

⚠️ Breaking Changes ⚠️
Requires Swift 5.1

Add vendor extensions to Content

Content gets vendor extensions (specification extensions) via a dict that can hold arbitrary additional properties.

Tons of additions, improvements, test coverage, and breaking changes.

⚠️ Breaking Changes ⚠️

• PathItem Parameter
• JSONReference
• JSONSchema

Fix annoying warnings and add integer expressibility to status codes.

• Fix annoying warnings from passing nil to string interpolation.
• Add integer expressibility for response status codes and add unit tests for Response file.

Make package available without OS X 10.13

OS X 10.13 is required for some conveniences I used for testing but the package works fine without it.

0.1.0

Merge branch 'master' of github.com:mattpolzin/OpenAPI