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



why the copy paste:
```python
if diff_line.startswith('+'):
    action = self._add_diff
elif diff_line.startswith('-'):
    action=self._remove_diff
action(line_no, diff_line.rstrip(), meta, squigly_line)
```