Fix installation of groff and follow Dockerfile best practices

[stilvoid]

The current Dockerfile does not install groff and doesn't follow Dockerfile best practice.

This builds a fully working container. I've set up an automated build at https://hub.docker.com/r/stilvoid/saws/.

[codecov-io]

Current coverage is 94.52%

Merging #75 into master will not affect coverage as of 3de77e5

@@            master     #75   diff @@
======================================
  Files           29      29       
  Stmts         1241    1241       
  Branches         0       0       
  Methods          0       0       
======================================
  Hit           1173    1173       
  Partial          0       0       
  Missed          68      68       

Review entire Coverage Diff as of 3de77e5

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[cliveza]

I submitted a follow up pull request to fix my error, but @stilvoid dockerfile is better, removing mine.

[stilvoid]

Thanks @cliveza. I looked for issues or pull requests related to this problem but couldn't find any.

[donnemartin]

Thanks @stilvoid @cliveza!

[stilvoid]

Strangely, I don't see these changes in the master branch any more. Has there been a force push since?

[donnemartin]

@stilvoid @cliveza DOH! I was trying a few things in the develop branch and intended to blow away just those changes. Looks like I accidentally toppled your changes in master, sorry!

I've hand merged the pull requests (it was a little messy) but we should be all set now.

To prevent similar issues in the future I set up branch protection. Actually, I went ahead and set up branch protection for all my other repos too.

Apologies for the inconvenience, and thanks for catching it.

[stilvoid]

No worries. I'd have happily rebased and resubmitted my PR but this works just fine :)

I'll update my fork so the automated build here is up to date.