Merge pull request adafruit#1201 from caternuson/clue_altimeter_update

CLUE altimeter update

Author: ladyada

CLUE_Altimeter/clue_altimeter.py

@@ -30,7 +30,8 @@
 clue._pressure.standby_period = 0x01  # 62.5 ms
 
 # restore saved sea level pressure from NVM
-clue.sea_level_pressure = struct.unpack("f", nvm[0:4])[0]
+slp = struct.unpack("f", nvm[0:4])[0]
+clue.sea_level_pressure = slp if 0 < slp < 2000 else STD_SLP
 
 # --------------------------------------------------------------------
 # D I S P L A Y    S E T U P