Calculate GC Percentage and output to stdout

[mndoucette]

Description

A feature was requested to calculate GC percentage from raw read files (.fastq). GC percentage calculation has been added and output is printed to stdout.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Tested using simulated read file with known GC counts (see data/sample.fastq)

Checklist:

• My code adheres to the repository style guide
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings
• New and existing tests pass locally with my changes