Docs updates: add installing, advanced recipes, remote gpio and remote recipes - wip

docs/recipes_advanced.rst

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+================
+Recipes (Simple)
+================
+
+.. currentmodule:: gpiozero
+
+The following recipes demonstrate some of the capabilities of the GPIO Zero
+library. Please note that all recipes are written assuming Python 3. Recipes
+*may* work under Python 2, but no guarantees!
+
+Travis build LED indicator
+==========================
+
+Use LEDs to indicate the status of a Travis build. A green light means the
+tests are passing, a red light means the build is broken:
+
+.. literalinclude:: examples/led_travis.py
+
+Note this recipe requires `travispy`_. Install with ``sudo pip3 install
+travispy``.
+
+Button controlled robot
+=======================
+
+Alternatively, use four buttons to program the directions and add a fifth
+button to process them in turn, like a Bee-Bot or Turtle robot.
+
+.. literalinclude:: examples/robot_buttons_2.py
+
+Controlling the Pi's own LEDs
+=============================
+
+On certain models of Pi (specifically the model A+, B+, and 2B) it's possible
+to control the power and activity LEDs.  This can be useful for testing GPIO
+functionality without the need to wire up your own LEDs (also useful because
+the power and activity LEDs are "known good").
+
+Firstly you need to disable the usual triggers for the built-in LEDs. This can
+be done from the terminal with the following commands::
+
+    $ echo none | sudo tee /sys/class/leds/led0/trigger
+    $ echo gpio | sudo tee /sys/class/leds/led1/trigger
+
+Now you can control the LEDs with gpiozero like so:
+
+.. literalinclude:: examples/led_builtin.py
+
+To revert the LEDs to their usual purpose you can either reboot your Pi or
+run the following commands::
+
+    $ echo mmc0 | sudo tee /sys/class/leds/led0/trigger
+    $ echo input | sudo tee /sys/class/leds/led1/trigger
+
+.. note::
+
+    On the Pi Zero you can control the activity LED with this recipe, but
+    there's no separate power LED to control (it's also worth noting the
+    activity LED is active low, so set ``active_high=False`` when constructing
+    your LED component).
+
+    On the original Pi 1 (model A or B), the activity LED can be controlled
+    with GPIO16 (after disabling its trigger as above) but the power LED is
+    hard-wired on.
+
+    On the Pi 3B the LEDs are controlled by a GPIO expander which is not
+    accessible from gpiozero (yet).