Removing errors and some warnings from build

[supuflounder]

• Arduino board: Feather HUZZAH32 (Adafruit #3405)

• Arduino IDE version (found in Arduino -> About Arduino menu): 1.8.5

• List the steps to reproduce the problem below (if possible attach a sketch or
  copy the sketch code in too): Build a project that uses Adafruit IO on a HUZZAH32

Here are the changes I made:

[brentru]

Thanks @supuflounder! I'm addressing some of these in #52 (the ones specifically regarding Adafruit_IO_Arduino)

[brentru]

Addressed the rest of these in adafruit/Adafruit_MQTT_Library#127. Closing...