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

replace with
```python
line.extend([GRAY, "\t(%d/%d)" % (len(files), num_files)])
if len(files) != num_files:
    line.append(', '.join(files))
line.append(ENDC)
```