Delete SimpleCamera (#2054)

* Remove SimpleCamera from arcade.camera's __init__.py

* Remove arcade/camera/simple_camera.py

* Update platformer tutorial step 7's .rst to account for Camera2D changes

* Use consistent code style for the class in step 7

Author: pushfoo

arcade/camera/__init__.py

@@ -14,7 +14,6 @@
 from arcade.camera.orthographic import OrthographicProjector
 from arcade.camera.perspective import PerspectiveProjector
 
-from arcade.camera.simple_camera import SimpleCamera
 from arcade.camera.camera_2d import Camera2D
 
 import arcade.camera.grips as grips
@@ -28,7 +27,6 @@
     'OrthographicProjector',
     'PerspectiveProjectionData',
     'PerspectiveProjector',
-    'SimpleCamera',
     'Camera2D',
     'grips'
 ]