Add example of library usage with Retrofit

[pwittchen]

Add example of library usage with Retrofit and update documentation.

It's related to issue #49.

[YuriHeupa]

Also waiting for this!

[Rainer-Lang]

Me too.

[pwittchen]

I remember about that. I just need to find some time for this. Recently, I've bumped library version and added new updates like support for Android N and better network monitoring, which are crucial enhancements in this project. Providing this example will be next on my list. :)

[epicstar]

I'm currently using this library with Retrofit + RxJava using Observable#retryWhen() using one of the older versions of ReactiveNetwork: https://github.com/rectangle-dbmi/Realtime-Port-Authority/blob/7.0.2/app/src/main/java/rectangledbmi/com/pittsburghrealtimetracker/BusMapFragment.java#L555

This will work when both of these two criteria are true:

1. the restish server cannot be reached (the retrofit observable throws an IOException)
2. when it is determined that this is due to a lost data connection on the phone side (though there is a bug where I'm not looking at SocketTimeoutException when I should... in other words, the app currently doesn't account for when the restish server is down and also thinks the phone connection is down... a bug)

I know that maybe people will be checking internet connection first then do their retrofit call, but I did my logic in reverse. My observable chain is currently running in an interval, and I wanted my interval to stop polling the restish server when the internet is gone, and restart the second when the internet is back. The lines of code above do exactly, that.

I hope that in the future, for the next rewritten feature of my app, I can a stack clicks for network calls when internet on the phone is somehow down and retry those click actions deriving from the logic above, too.

Currently, the rest of the code is a bit scary (because of my failure to use one of the MVVM patterns of Android... which will be fixed). I will be changing to the newer version of the library later AND will be using the internetConnectivityObservable when I have the time to change it.

[pwittchen]

I've added a simple example here: https://github.com/pwittchen/ReactiveNetwork#integration-with-retrofit.
It's valid for RxJava2.x version.