FIX: Suggested edits to the JOSS submission

[oesteban]

Updates the JOSS submission to incorporate the suggestions by @PeerHerholz.

References: openjournals/joss-reviews#3459
Resolves: #119.

[codecov-commenter]

Codecov Report

Merging #121 (0b58b61) into master (0b36f40) will not change coverage.
The diff coverage is n/a.

❗ Current head 0b58b61 differs from pull request most recent head 68679a4. Consider uploading reports for the commit 68679a4 to get more accurate results

@@           Coverage Diff           @@
##           master     #121   +/-   ##
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  Coverage   98.89%   98.89%           
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  Files          12       12           
  Lines        1084     1084           
  Branches      138      138           
=======================================
  Hits         1072     1072           
  Misses          6        6           
  Partials        6        6           

Flag	Coverage Δ
travis	98.89% <ø> (ø)

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[oesteban]

I have added one "audience" paragraph, following JOSS' guidelines.

[mgxd]

LGTM, looking a little closer at the requirements and I wonder if it would be good to mention nitransforms has been integrated into fMRIPrep. This is based on the bullet point:

Mention (if applicable) a representative set of past or ongoing research projects using the software and recent scholarly publications enabled by it.

[oesteban]

I think that's sensible, please pr against this branch (or commit directly to it)