Direct output of nf-core modules create-test-yml to tmp dir

[KevinMenden]

This directs the output of nf-core modules create-test-yml to a tmp directory.

Addresses #908 (partly)
The .nextflow* stuff is still not cleaned up but I'd say we can live with that.

PR checklist

• This comment contains a description of changes (with reason)
• CHANGELOG.md is updated
• If you've fixed a bug or added code that should be tested, add tests!
• Documentation in docs is updated

[codecov]

Codecov Report

Merging #1098 (fed86ce) into dev (afbed88) will not change coverage.
The diff coverage is 0.00%.

@@           Coverage Diff           @@
##              dev    #1098   +/-   ##
=======================================
  Coverage   70.36%   70.36%           
=======================================
  Files          36       36           
  Lines        4545     4545           
=======================================
  Hits         3198     3198           
  Misses       1347     1347           

Impacted Files	Coverage Δ
nf_core/modules/test_yml_builder.py	45.94% <0.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9ccd25c...fed86ce. Read the comment docs.

[ErikDanielsson]

Looks good to me!