Interpret format specifiers for size 1 arrays

[davidhassell]

Fixes #152

[codecov]

Codecov Report

Merging #153 (e008a1b) into master (f760739) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #153      +/-   ##
==========================================
+ Coverage   88.75%   88.76%   +0.01%     
==========================================
  Files         101      101              
  Lines       10505    10512       +7     
==========================================
+ Hits         9323     9330       +7     
  Misses       1182     1182              

Flag	Coverage Δ
unittests	88.76% <100.00%> (+0.01%)	⬆️

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Impacted Files	Coverage Δ
cfdm/data/data.py	84.61% <100.00%> (+0.18%)	⬆️

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[sadielbartholomew]

Resolves the corresponding issue and the test looks sufficiently thorough, with the possible exception I thought of being masked values, for which a warning does crop up with the PR as-is, so I have added a minor tweak as a suggestion to handle that.

Otherwise this is all good, so please merge when you are happy.