Fixed setCalibration

Fixed problem with setting calibration constants. Both values must be set in a single command.

Added Y4000 sonde support

Support for the Y4000 multi-parameter sonde added by Anthony Aufdenkampe.

Newest Modbus Manuals

Updates based on the newest Modbus manuals, acquired from Yosemitech Dec 2017.

Initial release

v0.1.6

Updated ReadMe, bumped version