Implement Pin number mapping (ie. 30 to P9-XX);
Fix error in pin gpio number comparison;
Update examples to use beaglebone pin constants;
Implement analog input for Pin class;
Add analog_read example;
Fix error in adc ADC_DIR constants;
Fix type error in adc_get_value;
Add ADC 12bit value mapping from [0,4095] to [0.0,1.0] range;
Add ADC threshold so AIN pins can be used for digital readings;
Fix beaglebone pin constants;
Update documentation;