Voltage regulator for primary battery

[robert-hh]

@danielm I have a good experience with a Pololu S7V8A adjustable up/down regulator. It delivers its output voltage (3..8v) for an input range between 2.6 and 11.8 V, which matches nicely the 2.8 to 4.1 range of the Lithium battery. It has an shutdown input too, in which case the quiescent current is determined by the 100k pullup resistor at that input.