Edit code to work with 0-voltage buttons on analog array

[MicDG]

Hello, in my analog array I have a button which brings the voltage to 0. To have it working this line in the _readButton() method of the BfButtonManager class must be changed from

if (z > this->_btnVoltageLowerBounds[_b] && z < this->_btnVoltageUpperBounds[_b]) {

to

if (z >= this->_btnVoltageLowerBounds[_b] && z < this->_btnVoltageUpperBounds[_b]) {

[mountain-lion-za]

My fork adds support for an ADC button that pulls down to 0.
See https://github.com/mountain-lion-za/ButtonFever
Pull request #8 open to merge back to this project, but no response from the original author yet.