iio.md: skeleton documentation

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

docs/iio.md

@@ -0,0 +1,24 @@
+iio				{#iio}
+===
+
+IIO is the kernel's framework for supporting sensors
+
+## 'RAW' access
+
+Mraa supports raw access
+
+###Channels
+
+###Attributes
+
+###Events
+
+###Triggers
+
+## Testing without hardware
+
+Create a dummy iio device
+$ modprobe iio_dummy
+
+Create a dummy iio event generator
+$modprobe iio_dummy_evgen