Address dependencies needed to allow Docker image to build

[jwalkerwelltok]

This is the smallest patch I could come up with to allow for this to build in Docker. This addresses issue #166. Both click and tabulate are imported in the application directly, so those libraries were added to dev-requirements.txt instead of tox-requirements.txt

[codecov-io]

Codecov Report

Merging #224 into master will not change coverage. The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #224   +/-   ##
=======================================
  Coverage   83.08%   83.08%           
=======================================
  Files          31       31           
  Lines        1969     1969           
=======================================
  Hits         1636     1636           
  Misses        333      333

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[jwalkerwelltok]

@andrewmchen, do you have a chance to review this? I ask because you were involved in discussion on #167