Build: Update dev dependencies (eslint, rollup, grunt, nyc)

No significant difference in the output, except a minor whitespace
improvement somewhere in Babel's helper functions.

```
--- qunit/qunit-main-branch.js
+++ qunit/qunit.js
@@ -37,7 +37,7 @@
   function _createForOfIteratorHelper(r, e) {
     var t = "undefined" != typeof Symbol && r[Symbol.iterator] || r["@@iterator"];
     if (!t) {
-      if (Array.isArray(r) || (t = _unsupportedIterableToArray(r)) || e  ) {
+      if (Array.isArray(r) || (t = _unsupportedIterableToArray(r)) || e) {
         t && (r = t);
```