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 
```python
cmap = {'-': RED, '+' : GREEN, '^': GREEN if line.startswith('+') else RED}
for i,s in enumerate(squilgly):
  if s == flag: continue
  chars.insert(i+compensator, ENDC)
  compensator += 1
  flag = s
  chars.insert(i+compensator, cmap(s))
```