Update Adafruit_BMP085_U.h

add new function: float seaLevelForAltitude(float altitude, float atmospheric, float temp);
which converts the measured pressure at a give altitude to sealevel-pressure.
This is useful, when you will use the BMP for weather-reporting.
Update Adafruit_BMP085_U.cpp

add new function: float seaLevelForAltitude(float altitude, float atmospheric, float temp);
which converts the measured pressure at a give altitude to sealevel-pressure.
This is useful, when you will use the BMP for weather-reporting.
Merge pull request #3 from kunosee/master

add another function, which will return seaLevelPressure for a given height