Illustrate case insensitivity option for `grep`

[ameynert]

How could the content be improved?

See comment from @ggrimes on #316

The lesson could also be use to illustrate grep options such as case insensitivity -i

grep single SraRunTable.txt 

vs

grep -i single   SraRunTable.txt 

and Whole-word match -w

grep ZDB16 SraRunTable.txt

vs

grep -w ZDB16 SraRunTable.txt

For the Writing for loops section

It work up to the following loop that extract the sample name from the fastq files and then add them to a seprate file

for file in *.fastq; do
  sample=$(basename $file .fastq)
  grep "$sample" ../sra_metadata/SraRunTable.txt >> metadata.txt
done

Which part of the content does your suggestion apply to?

Episode 4 - redirection