Code refactoring

[chfw]

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-io]

Codecov Report

Merging #19 into dev will increase coverage by 0.13%.
The diff coverage is 96.87%.

@@            Coverage Diff             @@
##              dev      #19      +/-   ##
==========================================
+ Coverage   97.52%   97.65%   +0.13%     
==========================================
  Files          12       12              
  Lines         646      641       -5     
==========================================
- Hits          630      626       -4     
+ Misses         16       15       -1     

Impacted Files	Coverage Δ
pyexcel_ods3/odsr.py	98.03% <90.00%> (-0.21%)	⬇️
pyexcel_ods3/odsw.py	100.00% <100.00%> (+1.81%)	⬆️
tests/test_ods_reader.py	100.00% <100.00%> (ø)
tests/test_writer.py	96.96% <100.00%> (-0.18%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 4771a4b...e69589d. Read the comment docs.