Add files to package.json and remove .npmignore and .dntrc

Author: vweevers

.dntrc

@@ -13,6 +13,13 @@
     "dependency-check": "dependency-check --no-dev .",
     "prepublishOnly": "npm run dependency-check"
   },
+  "files": [
+    "lib",
+    "CHANGELOG.md",
+    "CONTRIBUTORS.md",
+    "UPGRADING.md",
+    "sauce-labs.svg"
+  ],
   "dependencies": {
     "catering": "^2.0.0",
     "deferred-leveldown": "~5.3.0",