ENH: added a debug message to report details of the request to doi.org

[yarikoptic]

but also just want to see if CI is currently passing or not upon a PR

[coveralls]

Coverage increased (+0.1%) to 86.527% when pulling 2342923 on yarikoptic:enh-debug-msg into eca6ea9 on duecredit:master.

[codecov-io]

Codecov Report

Merging #165 into master will increase coverage by 0.17%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #165      +/-   ##
==========================================
+ Coverage   83.29%   83.46%   +0.17%     
==========================================
  Files          46       46              
  Lines        2382     2383       +1     
  Branches      259      259              
==========================================
+ Hits         1984     1989       +5     
+ Misses        325      322       -3     
+ Partials       73       72       -1

Impacted Files	Coverage Δ
duecredit/io.py	81.29% <100%> (+0.83%)	⬆️
duecredit/tests/test_api.py	91.39% <0%> (+2.15%)	⬆️

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[yarikoptic]

is still green - good