Add support for active high buttons

[bodgit]

Adds an additional constructor so you can create an active high button like:

ezButton button(pinNumber, INPUT, ACTIVE_HIGH);

The default is active low so this change shouldn't break existing code.

[uzi18]

@ArduinoGetStarted please merge

[ArduinoGetStarted]

@uzi18 I am going to update new version of this library, that will support more features