added question 3 and 4

wgs.sh

 
 # Question 3
 
+soft/megahit --k-list 21 --mem-flag 0 -1 EchE_R1.fastq.gz -2 EchE_R2.fastq.gz -o contigs
+
+# Question 4
+
+soft/prodigal -i contigs/final.contigs.fa -f fasta > genes.fna