Fix up some string concatenation, line length issues, etc.

[mulhod]

Closes #636

Mainly, this PR has to do with cleaning up some multi-line string concatenations (or removing them altogether when possible). There are a couple other randomish improvements I made as well (like reducing the length of some very long lines or lines where it was easy to do, removing unused parameters from a function used by a test, etc.).

[pep8speaks]

Hello @mulhod! Thanks for updating this PR.

• In the file tests/test_output.py:

Line 398:47: E741 ambiguous variable name 'l'

Comment last updated at 2020-11-18 15:53:42 UTC

[codecov]

Codecov Report

Merging #645 (45d13af) into main (48dc473) will not change coverage.
The diff coverage is 90.38%.

@@           Coverage Diff           @@
##             main     #645   +/-   ##
=======================================
  Coverage   95.11%   95.11%           
=======================================
  Files          27       27           
  Lines        3093     3093           
=======================================
  Hits         2942     2942           
  Misses        151      151           

Impacted Files	Coverage Δ
skll/learner/utils.py	94.94% <57.14%> (ø)
skll/experiments/__init__.py	95.19% <80.00%> (ø)
skll/learner/__init__.py	96.26% <93.33%> (ø)
skll/config/__init__.py	95.09% <100.00%> (ø)
skll/config/utils.py	95.65% <100.00%> (ø)
skll/data/writers.py	94.11% <100.00%> (ø)
skll/experiments/output.py	97.36% <100.00%> (ø)
skll/metrics.py	97.87% <100.00%> (ø)
...utils/commandline/compute_eval_from_predictions.py	97.18% <100.00%> (ø)
skll/utils/commandline/filter_features.py	98.41% <100.00%> (ø)
... and 9 more

---

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[mulhod]

Why the coverage check is failing I have no idea. When I click on the "Details" link, I don't see any change in coverage... Perhaps I'm not reading it correctly?

[desilinguist]

Looks great! Thanks for taking this on @mulhod!

[mulhod]

@bndgyawali If you get a chance, could you take a look at this? There are quite a few changes, but they are all cosmetic.