Merges two (or more) paired end FASTQ files together for combined mapping.
The files need to have the paired reads in the same order. They will be
written out as:

@name1
seq1
+
qual1
@name1
seq2
+
qual2
...

The merged file is written to stdout.

Usage: fastqutils merge {-slash} file1.fastq{.gz} file2.fastq{.gz} ...

-slash    Split the read name at a '/' (Illumina paired format)