Migrate tests from mocha and chai to node-tap (#83)

* Replace testing dependencies

- `mocha` with `tap`
- `chai-http` with `simple-get`

* Rewrite Validator tests to use tap

The original tests were testing Ajv functionality, which seems
unnecessary, so I've removed them.

* Rewrite middleware tests to use tap

* Rewrite integration tests to use tap

In the process of rewriting these tests I've added `name` as a
required property in the JSON schema and corrected the request
body which is being sent for a "valid" request.

* Remove glob from tap command in test run script

The `tap` CLI will automatically look in the `test/` directory.

* Update CI GitHub Actions workflow

Change to work with `tap`.

* Update npm lockfile

* Update ESLint configuration

The `no-shadow` rule has been disabled for tests, as when tests are
written using `tap`, the variable `t` is typically shadowed in
subtests.

Author: simonplend

.eslintrc.json

@@ -1,8 +1,7 @@
 {
 	"env": {
 		"es6": true,
-		"node": true,
-		"mocha": true
+		"node": true
 	},
 	"extends": [
 		"google",

.github/workflows/ci.yml

@@ -24,7 +24,5 @@ jobs:
       with:
         node-version: ${{ matrix.node-version }}
     - run: npm ci
-    - run: npx nyc mocha
-    - run: npx nyc report --reporter=lcov
-    - run: cat ./coverage/lcov.info > coverage.lcov
-    - run: npx codecov
+    - run: npm test
+    - run: npm test -- --coverage-report=text-lcov | npx codecov --pipe