Not teaching an async or routing library. about fcc-react-tests-module

[bonham000]

@ConradKay I think this is a great idea. The challenge Redux 12 actually does use Redux-Thunk to explain how asynchronous actions can work with Redux. But I think advanced topics like Redux-Saga, Rx, or routing would be good additions, along with testing.

However, eventually, these challenges will be merged into the main freeCodeCamp codebase. I think for the time being we should wait to make any substantial changes or additions to this React/Redux curriculum.

Another potential concern to be aware of is that any changes to a library could cause problems with challenges written before that change. We've already experienced that with these React challenges (React v15), even though React's API is pretty stable at this point. Other libraries (React Router, e.g.) have changed more frequently in the past few years). This is just another consideration that would need to be taken into account before committing to write challenges.