chore(TypeScript): refactor objects into classes

fix: `Nil`(null, undefined) now renders as empty string
change: `parser.parseValue()` renamed to `parser.parseOutput`
change: registered tags/filters become static and shared across different liquid instances

package.json

@@ -3,13 +3,11 @@
   "version": "7.0.0",
   "description": "Liquid template engine by pure JavaScript: compatible to shopify, easy to extend.",
   "main": "dist/liquid.common.js",
-  "module": "src/index.js",
   "browser": "dist/liquid.js",
-  "types": "src/index.d.ts",
   "scripts": {
     "lint": "eslint src/ test/ *.js",
-    "unit": "mocha test/unit",
-    "e2e": "mocha test/e2e",
+    "unit": "mocha -r ts-node/register -r tsconfig-paths/register test/unit/**.ts",
+    "e2e": "npm run build && mocha -r ts-node/register -r tsconfig-paths/register test/e2e/**/*.ts",
     "test": "npm run unit && npm run e2e",
     "coverage": "nyc --reporter=html npm run unit",
     "coveralls": "nyc report --reporter=text-lcov | coveralls",
@@ -42,6 +40,9 @@
     "@semantic-release/git": "^7.0.8",
     "@semantic-release/npm": "^5.1.4",
     "@semantic-release/release-notes-generator": "^7.1.4",
+    "@types/jsdom": "^12.2.2",
+    "@types/mocha": "^5.2.6",
+    "@typescript-eslint/eslint-plugin": "^1.3.0",
     "chai": "^4.2.0",
     "chai-as-promised": "^7.1.1",
     "coveralls": "^3.0.2",
@@ -60,7 +61,6 @@
     "nyc": "^13.1.0",
     "regenerator-runtime": "^0.12.1",
     "rollup": "^1.1.2",
-    "rollup-plugin-alias": "^1.5.1",
     "rollup-plugin-shim": "^1.0.0",
     "rollup-plugin-typescript2": "^0.19.2",
     "rollup-plugin-uglify": "^6.0.2",
@@ -69,6 +69,7 @@
     "sinon-chai": "^3.3.0",
     "supertest": "^3.4.2",
     "ts-node": "^8.0.2",
+    "tsconfig-paths": "^3.8.0",
     "typescript": "^3.3.3"
   },
   "release": {