- Added D4 and moved associated SD_CS so that they are paired within list
- Added D7 and SD_CD which is the SD Card Detect pin
- Added D8 and GREEN_LED
- Added RED_LED associated with D13
- Added Setup information regarding arm complier packages
* Always init SPI to 250k to start for SD cards.
* Add ability to configure byte written during read.
* Add ability to read and write to portions of buffers like existing I2C API.
Docs are here: http://tannewt-micropython.readthedocs.io/en/microcontroller/
It differs from upstream's machine in the following ways:
* Python API is identical across ports due to code structure. (Lives in shared-bindings)
* Focuses on abstracting common functionality (AnalogIn) and not representing structure (ADC).
* Documentation lives with code making it easy to ensure they match.
* Pin is split into references (board.D13 and microcontroller.pin.PA17) and functionality (DigitalInOut).
* All nativeio classes claim underlying hardware resources when inited on construction, support Context Managers (aka with statements) and have deinit methods which release the claimed hardware.
* All constructors take pin references rather than peripheral ids. Its up to the implementation to find hardware or throw and exception.
