update ls flag to sort by size

[raynamharris]

This is not necessary, but since we are talking about size, I think it would be nice to use the ls -S to sort by size. I chose to omit the h flag because the size difference is more noticeable in non-human readable form.

-rw-rw-r-- 1 dcuser dcuser 128M Oct  9 16:23 SRR2589044_2.fastq.gz
-rw-rw-r-- 1 dcuser dcuser 124M Oct  9 16:20 SRR2589044_1.fastq.gz
-rw-rw-r-- 1 dcuser dcuser  94M Oct  9 18:40 SRR2589044_1.trim.fastq.gz
-rw-rw-r-- 1 dcuser dcuser  91M Oct  9 18:40 SRR2589044_2.trim.fastq.gz
-rw-rw-r-- 1 dcuser dcuser  18M Oct  9 18:40 SRR2589044_1un.trim.fastq.gz
-rw-rw-r-- 1 dcuser dcuser 271K Oct  9 18:40 SRR2589044_2un.trim.fastq.gz

versus

-rw-rw-r-- 1 dcuser dcuser 134214678 Oct  9 16:23 SRR2589044_2.fastq.gz
-rw-rw-r-- 1 dcuser dcuser 129138426 Oct  9 16:20 SRR2589044_1.fastq.gz
-rw-rw-r-- 1 dcuser dcuser  97578370 Oct  9 18:40 SRR2589044_1.trim.fastq.gz
-rw-rw-r-- 1 dcuser dcuser  95396892 Oct  9 18:40 SRR2589044_2.trim.fastq.gz
-rw-rw-r-- 1 dcuser dcuser  18322107 Oct  9 18:40 SRR2589044_1un.trim.fastq.gz
-rw-rw-r-- 1 dcuser dcuser    277272 Oct  9 18:40 SRR2589044_2un.trim.fastq.gz