[FIX] Change os.basename to os.path.basename

[smeisler]

Addresses bug found in https://neurostars.org/t/attributeerror-module-os-has-no-attribute-basename/27604/2.

An instance of os.basename is leading to errors since it should be os.path.basename.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (b073fbf) 76.59% compared to head (3a9d9fa) 76.59%.

Files	Patch %	Lines
sdcflows/interfaces/fmap.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #419   +/-   ##
=======================================
  Coverage   76.59%   76.59%           
=======================================
  Files          32       32           
  Lines        2824     2824           
  Branches      373      373           
=======================================
  Hits         2163     2163           
  Misses        595      595           
  Partials       66       66           

Flag	Coverage Δ
unittests	∅ <ø> (∅)

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[mgxd]

LGTM, thanks!

[smeisler]

I realize I forgot to add myself to contributors list, will open a new PR for that