calculate chrM percent

Code from: https://yiweiniu.github.io/blog/2019/03/ATAC-seq-data-analysis-from-FASTQ-to-peaks/

Tested the correctness.

Usage

module load samtools/1.7
bam_chrM_percent.sh Hudep2_S120_GFP_neg_ARID3A_2.markdup.bam

output
------

Hudep2_S120_GFP_neg_ARID3A_2.markdup.bam : .43%

code @ github.