Set I2C clock to 1MHz for Adafruit Feather M0 (And presumably Arduino Zero)

[yngndrw]

Changed from the default I2C clock (100KHz ?) to 1MHz for SAMD Zero boards. Tested with an Adafruit Feather M0 Adalogger and an Adafruit FeatherWing OLED. I did try 3.4MHz but that speed didn't work.

See: https://www.arduino.cc/en/Reference/WireSetClock

[yngndrw]

Would need to be re-worked once #87 is merged.

[yngndrw]

Related to #68, but that PR is for a different speed and has different conditions.

[JamesHagerman]

Thank you for this even if it hasn't been merged!

It's easy enough to change this in your own script by adding the same code:

  #ifdef ARDUINO_SAMD_ZERO
   Wire.setClock(1000000u); // Fast mode plus: 1MHz
  #endif

Which makes things on the Feather M0 boards pretty fast!

[PaintYourDragon]

Thanks for the pull request! Similar functionality has been incorporated in the latest release.