update IO TLS fingerprint

Update Adafruit_MQTT_Client.cpp to remove use of min()

see https://github.com/adafruit/Adafruit_MQTT_Library/issues/106  for discussion of link failures after upgrading esp8266 community library  BSP to version 2.4.0  --  removing the use of min() allows for successful compilation,link and execution.

Replace call to min() with ternary statement to accomplish same action.

Fix min() usage when using STL C++

Signed-off-by: Frederic.Pillon <frederic.pillon@st.com>

Use correct separator in keywords.txt

The Arduino IDE requires the use of a tab separator between the name and identifier. Without this tab the keyword is not highlighted.

Reference: https://github.com/arduino/Arduino/wiki/Arduino-IDE-1.5:-Library-specification#keywords

Adafruit IO MQTT Callbacks

Remove FlashStringHelper Methods