add histogram reader
This adds a default reader for histograms, as well as a sanity check for those histograms (i.e. second order moment computed on the fly is compared with second order moment obtained from the probability density function).
This adds a default reader for histograms, as well as a sanity check for those histograms (i.e. second order moment computed on the fly is compared with second order moment obtained from the probability density function).