allow trailing options, get_data(...keep_trailing_empty_cells=…

[chfw]

…True). fix #86

With your PR, here is a check list:

• Has test cases written?
• Has all code lines tested?
• Has make format been run?
• Please update CHANGELOG.yml(not CHANGELOG.rst)
• Passes all Travis CI builds
• Has fair amount of documentation if your change is complex
• Agree on NEW BSD License for your contribution

[codecov-commenter]

Codecov Report

Merging #88 into dev will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev      #88      +/-   ##
==========================================
+ Coverage   97.02%   97.03%   +0.01%     
==========================================
  Files          50       50              
  Lines        3225     3236      +11     
==========================================
+ Hits         3129     3140      +11     
  Misses         96       96              

Impacted Files	Coverage Δ
pyexcel_io/reader.py	97.40% <ø> (ø)
pyexcel_io/sheet.py	98.78% <100.00%> (+0.04%)	⬆️
tests/test_csv_book.py	100.00% <100.00%> (ø)

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