amperage underflow fix

README: added Amazon purchase link for the display

updated README (2)

SHOW_AVG_CELL_VOLTAGE true by default

Session data (#20)

* session data

* text screen: properly formatted time

* bug fix: trip distance not saved to EEPROM

* bug fix: reset time elapsed

* text screen: dim capacity % when resetting

* simple vertical screen: do not dim battery voltage

* text screen: add avg speed

* text screen: fault code last

README: VESC config

improved release script

release script