chore(package): update ava to version 0.19.0 (#25)

Author: greenkeeper[bot]

package.json

@@ -8,7 +8,7 @@
   },
   "bugs": "https://github.com/static-dev/source-loader/issues",
   "devDependencies": {
-    "ava": "^0.18.2",
+    "ava": "^0.19.0",
     "coveralls": "2.x",
     "nyc": "10.2.0",
     "standard": "10.0.0",