Update React Readme

TodoMvc example for scalajs-react

Close #1459

Polymer 1.0 demo cleanup

The app is getting outdated and is these days even totally broken sowe
decided to remove it, till someone volunteers to maintain it and PRs it
back with all remaining issues fixed.

There was an open PR with some updates but it went inactive:
https://github.com/tastejs/todomvc/pull/1241

Close #1241
Fix #1222
Ref #1234
Ref #1110

Update index.html

comment was using `todos` whereas the code is using `todos-react-backbone` - i opted for a non-breakable comment instead

🍕🌟Polymer 1.0 🌟🍕

* Update for spec complience
* Polymer 0.5 -> 1 changes

fix checkbox bug in the mithril TodoMVC example

added an error callback to the hidden check of the clear completed items button. This was done so that frameworks like mithril who remove elements from DOM in stead of putting css-classes like .hidden on elements get through the test suite

The bug is caused by lack of keying.

To reproduce the bug:
1. Open the app
2. Create at least two tasks
3. Complete all tasks
4. Go to the completed view
5. uncheck the top item
6. Voilá, see how the first item in the list now has an unchecked checkbox

Fix typo

Fix broken links

Remove deprecated code and concepts from Backbone.Marionette example

🚀 run jscs over tests

ref:
https://github.com/tastejs/todomvc/commit/07353bcd844b41a2bf214d9c42845b65157a8bf7#commitcomment-13197635
https://github.com/tastejs/todomvc/commit/abee8bdedb4913a6f70b4ad5167fad16ad333def

Ref 07353bcd

This one is exactly the same as the one in the root directory so there's
no reason for it to be in the riot example folder too.

fix homepage link for riotjs.com