HMR version 4 update

[rllola]

There is a new version of HMR which is in Beta now. The documentation might need to be updated. It is not working the same way anymore (see https://github.com/gaearon/react-hot-loader/tree/next).

It also break HMR for me with electron. See this example repo : https://github.com/rllola/hmr-example-issue

Before it was the instanceOf which was broken. Now, it is the re-rendering of the html code which doesn't work. When changing code it doesn't show the modification..