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
 - [ ] add documentation / docstrings
 - [ ] figure out how to display added/removed spaces



@boegel If extract_file were to use the tarfile module, this would be very easy I suppose. I understand, however, that currently this is impossible (due to 2.4 requirements).