feat: enable onload callbacks (#414)

* refactor(examples): run ssr example from server

* chore: switch to babel for build

buble complains too much

* feat: enable loaded callbacks

feat: add skip option

* examples: add async-callback browser example

* examples: fix server

* examples(ssr): add reactive script with callback

* fix: also skip on ssr

* chore: remove unused var

* feat: only add mutationobserver if DOM is still loading

feat: disconnect mutation observer once DOM has loaded

* examples: pass vmid to loadCallback instead of el

* feat: also support load callbacks for link/style tags

* test: add unit tests for load

* test: add load e2e test

* chore: fix lint

* chore: remove unused files

* test: fix e2e load callback test

* test: fix attempt

* examples: ie9 compatiblity

destructuring doesnt work in ie9

* fix: add onload attribute on ssr

dont rely on mutationobserver

* chore: lint ci conf

* refactor: remove loadCallbackAttribute config option

test: fix coverage for load

* test: improve coverage

* fix: only use console when it exists (for ie9)

* chore: fix coverage

examples/_static/user-2.js

@@ -0,0 +1,23 @@
+window.users.push({
+  'id': 2,
+  'name': 'Ervin Howell',
+  'username': 'Antonette',
+  'email': 'Shanna@melissa.tv',
+  'address': {
+    'street': 'Victor Plains',
+    'suite': 'Suite 879',
+    'city': 'Wisokyburgh',
+    'zipcode': '90566-7771',
+    'geo': {
+      'lat': '-43.9509',
+      'lng': '-34.4618'
+    }
+  },
+  'phone': '010-692-6593 x09125',
+  'website': 'anastasia.net',
+  'company': {
+    'name': 'Deckow-Crist',
+    'catchPhrase': 'Proactive didactic contingency',
+    'bs': 'synergize scalable supply-chains'
+  }
+})