Generates a 2d histogram from paired count data.
``` USAGE: hist2d [OPTIONS]
FLAGS: -h, --help Prints help information -V, --version Prints version information
OPTIONS: -n, --nbins Number of bins in each dimension (memory use will be O(N^2)) [default: 1000] -s, --sep Separator for output [default: ]
ARGS: Input file (with counts in 2nd and 3rd columns) ```