Add script to create separate fasta for each cluster

[ksahlin]

The script should take the tsv file generated by isONclust and output reads into fasta or fastq files with reads belonging to each cluster. The script should take a parameter -n [int] that tells the script the smallest clusters that should be output, and a --fastq or --fasta flag for the output format.

[ksahlin]

fixed in version 0.0.3