Update iv_scans.py
Updated the iv_scan script to produce plots of the sensor temperature as a function of the high voltage. Should be simple to use as it is based off the current iv_scan method.
To Use: call tv_scan(iv_file, ref_file, sensor_id, yLow = -15, yHigh = -5) which returns the data plot as element 0 and the reference and element 1. This is the same as for iv_scan(iv_file, ref_file, sensor_id) except it no longer returns the mean temperatures