Smoothed histogram methods more consistent with Python

Smoothed NetEMD calculations now use the same variance calculation as the Python code. For our set of random test networks, the R and Python smoothed NetEMDs are almost identical for graphlet orbits up to 4 nodes (to at least 4 decimal places for all but one pair).

Note: R and Python smoothed NetEMDs are still significantly different for graphlet orbits up to 5 nodes. Investigation of this difference continues.