Minor clean-up

Expand gitignore to include the usual py developing stuff, add an
__init__ to make this a legitimate package, move GPIO initialization
into the package init, import all stuff from input and output devices in
the package to enable the access demonstrated in the example, remove a
duplicate method from LightSensor, and make motion_detected a property
(for consistency with is_active which it presumably parallels).

gpio_components/__init__.py

@@ -0,0 +1,20 @@
+from RPi import GPIO
+
+GPIO.setmode(GPIO.BCM)
+GPIO.setwarnings(False)
+
+from .input_devices import (
+    InputDeviceError,
+    InputDevice,
+    Button,
+    MotionSensor,
+    LightSensor,
+    TemperatureSensor,
+    )
+from .output_devices import (
+    OutputDevice,
+    LED,
+    Buzzer,
+    Motor,
+    )
+