Please make MICROSECONDS_FOR_180 and MICROSECONDS_FOR_0 configurable per servo

[sglebs]

I suggest making ServoManager::createServo take 2 extra params: "microseconds for 0" and "microseconds to 180". As default / backwards compatibility in the API, when nothing is passed you can use the current hardcoded constants. Storing them in instance variables allows for this flexibility. Other libs have a similar approach, see https://www.arduino.cc/en/Reference/ServoAttach