Rather than passing multiqc a directory of fastqc reports, pass it a collection of files

[stenglein-lab]

This is the current code:

multiqc -n "initial_qc_report.html" -m fastqc ${params.initial_fastqc_dir}

This is producing this error when running with -profile test

 Usage: multiqc [OPTIONS] <analysis directory>
  
  Error: Invalid value for '<analysis directory>': Path 'test_results/initial_fastqc/' does not exist.
  
  This is MultiQC v1.11
  
  For more help, run 'multiqc --help' or visit http://multiqc.info

The issue is that test_results/initial_fastqc is not a valid path relative to the work directory (pwd) in which multiqc is being run.

To solve this issue, either need to provide the directory from a path channel, or could pass the files, use collect() operator, then stage them in a local sub-dir.

[stenglein-lab]

Implementing #18 will accomplish this.