Add FiscalDay

[nicmendoza]

Hey @adamjstewart here's a possible implementation. Let me know what you think. I can add documentation if/when you feel good about the PR.

[codecov-io]

Codecov Report

Merging #13 (44a8f6d) into master (c03bc22) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##            master       #13    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files            1         1            
  Lines          364       485   +121     
==========================================
+ Hits           364       485   +121     

Impacted Files	Coverage Δ
fiscalyear.py	100.00% <100.00%> (ø)

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[adamjstewart]

Since there is overlap between this and your FiscalMonth PR, I'm going to focus on reviewing the other PR first.

[nicmendoza]

Merged master, so should be good to review now.

[nicmendoza]

Added some simple documentation.

Does it make sense to add sections for FiscalMonth and FiscalDay to the readme? Not sure why the thought didn't occur to me with the last PR, but even if it's a bit redundant it might help someone identify that the library is relevant for their use case.

Also, I added very subtle documentation for the isleap attribute I needed to add to FiscalYear. I'm not sure anyone will ever find it terribly useful, but it felt weird not documenting it so I sort of snuck it into the end of the example for FiscalYear.

[adamjstewart]

Does it make sense to add sections for FiscalMonth and FiscalDay to the readme?

Yes, please add to the README.rst and basics.rst, either in this PR or a follow-up PR.

Also, I added very subtle documentation for the isleap attribute I needed to add to FiscalYear. I'm not sure anyone will ever find it terribly useful, but it felt weird not documenting it so I sort of snuck it into the end of the example for FiscalYear.

I think that's good. It will also appear in the Sphinx-generated API docs.