Updated project structure and some file names.

Restored `requirements.txt`

Updated `setup.py` to include new repository url and contact details.

Moved the rtsp code from `record` to `stream`.

Updated project structure to make it more readable and developer friendly - moved mixins to the `mixins` package, moved handlers to the `handlers` package.

Moved files not belonging to anything in particular to the `util` package.

Updated `camera` class to also defer login call.

Deleted unused files like `config_handler`.

examples/basic_usage.py

@@ -0,0 +1,11 @@
+import reolinkapi
+
+if __name__ == "__main__":
+    cam = reolinkapi.Camera("192.168.0.102", defer_login=True)
+
+    # must first login since I defer have deferred the login process
+    cam.login()
+
+    dst = cam.get_dst()
+    ok = cam.add_user("foo", "bar", "admin")
+    alarm = cam.get_alarm_motion()