Re-implement React Hot Loader

[tech4him1]

React Hot Loader (and HMR in general) was removed in v1.0 since it was not working correctly. There were also some bugs with our transpiler that should both be fixed in RHL v4 (#765 (comment)). We should try to re-add this once it gets stable and working.

[tech4him1]

gaearon/react-hot-loader#703 explains the basic changes made to allow v4 work better.

[theKashey]

React-hot-loader v4.0.0-beta16(aka "next") is super stable and just working.

[erquhart]

Awesome, thanks for the heads up @theKashey

[tech4him1]

Caleb @tech4him1 Mar 31 09:24
@theKashey I'm getting back around to implementing RHL v4. Should the hot(module) wrapper be around any Redux Provider's, or just around the root App itself? Thank you!

Anton @theKashey Mar 31 16:13
Should be on top paths you gonna change. Root App is "on top" enought, @tech4him1, but dont use hot and react-dom/mount in one file.