Before the 1.4 update you could just write:
.observeOn(AndroidSchedulers.mainThread())
and import rx.android.schedulers.AndroidSchedulers; but now I can not make this work.
Is this moved / removed or does it exist another implementation now to get similar effect?
The library no longer relies on RxAndroid.
Make sure that you've put compile 'io.reactivex:rxandroid:XXX'
in your build.gradle, if you want to use it's classes in your code.
It's not a good pracitse to rely on tranitive dependencies, you should declare them on your own.