replace STARFUSION_DOWNLOAD with UNTAR_STARFUSION

[anoronh4]

Addresses #98.

Switched local module STARFUSION_DOWNLOAD to nf-core module untar (process alias UNTAR_STARFUSION)

It was possible to set this up "offline" if you run this "online" the first time, but it could be faster just to allow all sources references to be local and never require an online run to get set up.

PR checklist

• This comment contains a description of changes (with reason).
• If you've fixed a bug or added code that should be tested, add tests!
• If you've added a new tool - have you followed the pipeline conventions in the contribution docs
• If necessary, also make a PR on the mskcc/forte branch on the nf-core/test-datasets repository.
• Make sure your code lints (nf-core lint).
• Ensure the test suite passes (nextflow run . -profile test,docker --outdir <OUTDIR>).
• Usage Documentation in docs/usage.md is updated.
• Output Documentation in docs/output.md is updated.
• CHANGELOG.md is updated.
• README.md is updated (including new tool citations and authors/contributors).