Move to a modern testing infrastructure

Use Jest as test framework, and restructured ESLint config files so it applies to each directory separately.

Author: ishitatsuyuki

.eslintrc-node.js renamed to .eslintrc.js

@@ -19,6 +19,8 @@ module.exports = {
     "camelcase": "off",
     "no-var": "error",
     "prefer-const": "error",
+    "array-bracket-spacing": ["error", "always", {"objectsInArrays": false}],
+    "object-curly-spacing": ["error", "always"],
 
     // Override some eslint base rules because we're using node.
     "no-console": "off",