added a temporary fix for low-voltage detection on unplugging the usb
improved the delay in read_adc.  This gives more headroom for inconsistency between devices
Merge branch 'whb'
standardized sections, spacing.  prep for changes to low_voltage
Updated readme with a note on low battery delay
Added a note on battery monitoring progress
corrected some documentation in avr_voltage_test
low battery detection level is only set when unglugged from the USB
moved accelerometer_readings into experiments, added voltage_readings to experiments
removed note on battery power estimation