CI: make check-before-commit on Travis

[effigies]

Summary

Adds a make check-before-commit test to Travis, to verify that no changes are made to the working directory. This will help catch situations where people fail to run make specs, but it doesn't cause an error (e.g., adding an input) and when a test pollutes the repository with what should be temporary files.

Closes #2967.

List of changes proposed in this PR (pull-request)

• New Travis test
• Some cleanups from running locally, including a bunch of warnings about regexes

Acknowledgment

• (Mandatory) I acknowledge that this contribution will be available under the Apache 2 license.

[codecov]

Codecov Report

Merging #3066 into master will increase coverage by <.01%.
The diff coverage is 25%.

@@            Coverage Diff             @@
##           master    #3066      +/-   ##
==========================================
+ Coverage    67.7%   67.71%   +<.01%     
==========================================
  Files         344      344              
  Lines       44112    44165      +53     
  Branches     5563     5585      +22     
==========================================
+ Hits        29866    29905      +39     
- Misses      13481    13489       +8     
- Partials      765      771       +6

Flag	Coverage Δ
#smoketests	50.31% <0%> (ø)	⬆️
#unittests	65.13% <25%> (+0.01%)	⬆️

Impacted Files	Coverage Δ
nipype/interfaces/fsl/utils.py	70.35% <ø> (ø)	⬆️
nipype/interfaces/io.py	59.26% <ø> (ø)	⬆️
nipype/interfaces/utility/base.py	87.5% <ø> (ø)	⬆️
nipype/interfaces/image.py	73.41% <ø> (ø)	⬆️
nipype/interfaces/afni/utils.py	81.89% <0%> (ø)	⬆️
nipype/interfaces/diffusion_toolkit/dti.py	63.88% <0%> (ø)	⬆️
nipype/interfaces/dipy/tracks.py	31.11% <0%> (-0.56%)	⬇️
nipype/pipeline/engine/utils.py	80.76% <100%> (ø)	⬆️
nipype/pipeline/plugins/multiproc.py	81.39% <0%> (-3.18%)	⬇️
nipype/__init__.py	65.07% <0%> (+3.17%)	⬆️

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[oesteban]

Looks great, left just a minimal suggestion to only run the specs.