atmel-samd: Clean up leftovers from QTouch.

travis: turn off artifact debug.

Correct PulseOut example code

Split up nativeio.

This was done to allow greatly granularity when deciding what functionality
is built into each board's build. For example, this way pulseio can be
omitted to allow for something else such as touchio.

atmel-samd: Update Feather M0 Express USB pid.

Add PulseIn support which can be used to measure a series of pulse wi…

…dths.

This is useful for infrared input and DHT sensors.

shared-bindings: Fix two more try_locks. Copy and paste failed me.

ESP8266: Stop supporting 400khz neopixels through old esp module API.

It still accepts the parameter for backwards compatibility and to
provide a good error when it can't work.

Using the `neopixel_write` module instead is recommended because its
available on all CircuitPython supported ports.

Switch design guide to rST so that the table works. Also add details …

…based on more feedback from @deshipu. Thanks!

atmel-samd: Fix neopixel timing by forcing the NVM cache to be determ…

…inisticly timed. Otherwise, bit order changes code timing. Fixes adafruit#74