Add fiscal_month attribute to FiscalDateTime and FiscalDate

[nicmendoza]

This PR specifically adds a fiscal_month attribute (and does not add a correspondingFiscalMonth object). I can follow up with fiscal_week and fiscal_day if desired, but I really needed this functionality for my use case and I'm hoping this PR stands on its own. It's pretty simple, and I think the approach could be quickly adapted to those two additional calculations if/when desired.

Please let me know if the PR is missing anything.

[nicmendoza]

@adamjstewart is it possible re-running the build could resolve this issue? If I understand the logs, it seems like there's a plugin version resolution conflict with pytest specifically on Python 3.5 but the build+test are succeeding otherwise.

[nicmendoza]

Added a minor commit to re-trigger the build ☝

[codecov-io]

Codecov Report

Merging #11 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #11   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines          266       269    +3     
=========================================
+ Hits           266       269    +3     

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

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[nicmendoza]

Had to pin pytest and pytest-mock to old versions to maintain support for python 2 .7 (assuming that's still a requirement)

[adamjstewart]

Hi @nicmendoza, thanks for the contribution!

First impression: I like it, and I think the way you have things implemented looks correct. I'll go over this in more detail over the next couple of days.

With regards to the pytest issue: I think pinning the version is the right thing to do. We don't use any new features of PyTest anyway. I would like to continue to offer Python 2 support because a lot of people are stuck with Python 2, especially in industry where they can't update their own computers. I use a couple of supercomputing clusters that are still stuck on Python 2.6 unfortunately. I've thought about dropping support for Python 2, 3.0-3.4 so that I can add type hints, but so far there hasn't been any demand for it.

[adamjstewart]

Just a few minor suggestions, otherwise LGTM!