Unittest py37 support

[keigohtr]

What is this PR for?

Support python 3.7.
Need to upgrade pyyaml library to 3.13.

This PR includes

• Support python 3.7
• Upgrade libraries
• Move test for calculating an appropriate coverage

What type of PR is it?

Feature

What is the issue?

N/A

How should this be tested?

python -m unittest

[keigohtr]

Related to rekcurd/rekcurd-python#28 rekcurd/python-client#17

[codecov-io]

Codecov Report

Merging #60 into master will decrease coverage by 2.77%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #60      +/-   ##
==========================================
- Coverage   81.96%   79.18%   -2.78%     
==========================================
  Files          30       36       +6     
  Lines        1397     1595     +198     
==========================================
+ Hits         1145     1263     +118     
- Misses        252      332      +80

Impacted Files	Coverage Δ
drucker_dashboard/_project.py	100% <0%> (ø)
drucker_dashboard/server.py	89.36% <0%> (ø)
drucker_dashboard/drucker_dashboard_client.py	69.69% <0%> (ø)
drucker_dashboard/__init__.py	100% <0%> (ø)
drucker_dashboard/app.py	0% <0%> (ø)
drucker_dashboard/_version.py	100% <0%> (ø)

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[yuki-mt]

@keigohtr Can you merge master branch and move drucker_dashboard/test/test_api_evaluation.py to test/test_api_evaluation.py because test_api_evaluation.py was added and test_api_application.py & test_api_service.py were removed in #55 ?
I don't know why no conflict occurs in this PR...

[keigohtr]

@yuki-mt I have rebased this.
Since test_api_application.py & test_api_service.py are restored, I deleted these files by hand.

[yuki-mt]

LGTM!