Cleared compiler warnings
 - begin() does not return a value -- changed the return type to "void"
 - explicitly cast initialization value to float
 - used binary constant from Arduino's binary.h, instead of relying on gcc compiler
Merge branch 'master' of https://github.com/ms-iot/HTU21D_Breakout into ms-iot-master
Merge branch 'ms-iot-master'