Feature/add review pr option

use `./eb --review-pr 1017 -D | less -R` to try this out.
TODO:
 - [ ] Compare with other files found in the same PR
 - [ ] add legend on top
 - [x] add documentation / docstrings
 - [x] figure out how to display added/removed spaces



if you attempt `return multi_diff(easyconfig, listing, colored)` and print the result at the calling function,
that would reduce the LOC; is that beneficial in any kind of way or, it's more clumsy?