heatwaveR: A central algorithm for the detection of heatwaves and cold-spells

This release features many bug fixes throughout. It also endeavored to bring the naming conventions for the arguments in the functions more in line with the Python version of the code. A large addition to this version has been the allowance of a second climatology/threshold in the calculation of heatwaves and cols-spells. One potential backwards compatibility breaking change has been that by default the var column is no longer output from ts2clm(). One must now provide the argument var = TRUE.