Extend TestInvisibleInk and fix TestDigramCounter

[JoseALermaIII]

Summary

Adds functional test to TestInvisibleInk, fixes cross-platform test inconsistencies in TestDigramCounter, and adds PR template.

Description

Rather than manually changing the invisible ink color to red, running the demo main function, and checking the file, the color of the unit test's encrypted message can be checked using python-docx. It's kind of a test-ception importing python-docx to load the test file and check its color, but it ensures that even the encrypted message's color is correct.

The problem with including a file system word dictionary in unit tests is that not all file systems have the same word dictionary, much less in the same location. While running tests in Debian, the word dictionary ended up being in the same location (luckily), but had different words in it. The demo main function's word dictionary file path is now patched to use a test word dictionary. This should also make the tests run marginally faster.

The running gag gone wild has become so frequent that I have to acknowledge I make more PRs than I intended to. A PR template is now available to make my pseudo-blog more efficient for myself and to allow others to provide any optimizations they know of.

Having that said, I know I said in #1 that a PR seems unnecessary and wasteful; however, I must emphasize that this is one of the most important steps to foster a community of completeness and openness ever.

Team Notifications

Me, myself, and I

[JoseALermaIII]

Don't know if the PR template is a feature per se, but at least the bugs are fixed and the testing is more complete.