Switch test framework to ava

Should match datasheet-server.

package.json

@@ -7,7 +7,7 @@
   "scripts": {
     "dev": "webpack-dev-server --content-base static --mode development",
     "build": "NODE_ENV=production webpack --mode production",
-    "test": "./node_modules/mocha/bin/mocha"
+    "test": "npx ava --verbose"
   },
   "dependencies": {
     "babel-polyfill": "^6.26.0",
@@ -33,6 +33,7 @@
     "@babel/core": "^7.1.2",
     "@babel/preset-env": "^7.1.0",
     "@babel/preset-react": "^7.0.0",
+    "ava": "1.0.0-beta.8",
     "babel-loader": "^8.0.4",
     "css-loader": "^1.0.0",
     "file-loader": "^2.0.0",
@@ -46,5 +47,10 @@
     "webpack": "^4.20.2",
     "webpack-cli": "^3.1.2",
     "webpack-dev-server": "^3.1.9"
+  },
+  "ava": {
+    "files": [
+      "test/**/*.js"
+    ]
   }
 }