Add coverage report for this repository (#57)

[robinmatz]

Closes #57

Todo:

• 1# Increase code coverage
• 2# Create profile for Mainframe3270 on Codecov.io (requires project maintainer)
• 3# Update URL in Codecov badge in README.md. Depends on 2#. Will be done in different PR after merge.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (master@ba9c5ee). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #58   +/-   ##
=========================================
  Coverage          ?   94.77%           
=========================================
  Files             ?        4           
  Lines             ?      574           
  Branches          ?      105           
=========================================
  Hits              ?      544           
  Misses            ?       26           
  Partials          ?        4           

Flag	Coverage Δ
acceptance	79.26% <0.00%> (?)
unit	87.80% <0.00%> (?)

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[robinmatz]

Hey @samuelpcabral , this PR can now be merged.

Once in master, the dashboard on codecov should be updated. Then, we will also be able to update the codecov badge.