Uses samtools pileup to get the read counts for each base in the genomic position specified
get_read_counts(chr, pos, bam, tag = "", min_base_quality = 20,
max_depth = 1e+05, min_mapq = 30)chromosome name
genomic coordinate
path to bam file
the RG tag if the bam has more than one sample
minimum base quality for a read to be counted
maximum depth above which sampling will happen
the minimum mapping quality for a read to be counted
a list, number of reads for each of the four basepairs