feat(project): simplify setup

* drop development / testing builds of library
* consume lib / tests via esm
* simplify rollup config

Author: nikku

package.json

@@ -18,14 +18,14 @@
     "jsondiffpatch": "./bin/jsondiffpatch"
   },
   "scripts": {
+    "all": "run-s build test",
     "build": "rollup -c",
-    "build-dist": "rollup -c rollup-dist.config.js",
     "test-browser": "gulp test-browser",
     "lint": "eslint .",
     "bump": "gulp bump",
     "test": "nyc mocha",
     "watch": "nodemon --exec \"mocha\"",
-    "prepublish": "npm run build && npm run build-dist",
+    "prepublishOnly": "npm run all",
     "cover-report": "open coverage/lcov-report/index.html",
     "cover-publish": "nyc mocha && codeclimate < coverage/lcov.info"
   },
@@ -62,10 +62,12 @@
     "eslint-plugin-node": "^5.2.1",
     "eslint-plugin-promise": "^3.6.0",
     "eslint-plugin-standard": "^3.0.1",
+    "esm": "^3.0.25",
     "istanbul": "^0.4.5",
     "mkdirp": "^0.5.1",
     "mocha": "^5.0.0",
     "nodemon": "^1.17.1",
+    "npm-run-all": "^4.1.2",
     "nyc": "^11.4.1",
     "prettier": "^1.10.2",
     "rollup": "^0.54.1",