Fix for Application.isPlaying exception

See neuecc/UniRx/issues/33. Application.isPlaying cannot be accessed
from a worker thread. Workaround with a new ScenePlaybackDetector class.
The PostProcessScene callback is called when a scene starts. The
playmodeStateChanged event detects when a scene stops and is subscribed
to when the Unity Editor is launched.
Add ScenePlaybackDetector to project file, revert to original codestyle without explicit modifiers
Merge pull request #2 from movrajr/master

Fix for Application.isPlaying exception