Doc incorrect

[rnjv]

Pls modify

python reads_to_ctg_map.py /path/to/lib1_A.fq /path/to/lib1_B.fq /path/to/contigs.fasta --threads N

to

python reads_to_ctg_map.py /path/to/lib1_A.fq /path/to/lib1_B.fq /path/to/contigs.fasta /path/to/output --threads N

Cost me a few core hours on each library, It started to index the second library!