Create Test case for config files

[furtib]

Why:
We want to support config files; we should test for them.
What:

• Test whether every rule that takes a config file as an argument acts on the content of said config file

Addresses:
#30
Test for #102

[Szelethus]

The patch overall looks OK, but can you beef up the comments a bit? Something like this:

Set to true -> Set to true after fix; should've copied the input config file to bazel-bin
Set to 0 -> Set to 0 after fix; the config file should've explicitly disabled the division-by-zero checker, but the file is unrecognized by per-file analysis

Also, I'm not sure how important it is to check the first lines of the original/copied config files.

[furtib]

I'm pretty sure that I'm comparing the whole file contents, not just the first line.
https://docs.python.org/3/tutorial/inputoutput.html#:~:text=To%20read,returned
Although this part might not be so useful after all.

[Szelethus]

LGTM! I won't annoy you to death with my nits (we will delete them in a followup patch anyways), so I'll leave it to you how much you want to fancy them up. The nits were mainly meant as a general advice on how these comments would be ideal if you were to write a similar patch in the future.