Added `Observable behaviour` to Readme. https://github.com/Polidea/RxAndroidBle/issues/187
Added `Observable behaviour` to Readme. https://github.com/Polidea/RxAndroidBle/issues/187

Reviewers: michal.zielinski, pawel.urban

Reviewed By: pawel.urban

Differential Revision: https://phabricator.polidea.com/D2346

Polidea/RxAndroidBle,Polidea/RxAndroidBle,Polidea/RxAndroidBle