Make Err.unwrap traceback better for debugging

[kykosic]

Example:

from pycats import Result


@Result.wrap
def divide(a, b):
    return a / b


d = divide(2, 0)

d.unwrap()

Will give a traceback like:

---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
<ipython-input-1-e472ddea34ee> in <module>
      9 d = divide(2, 0)
     10 
---> 11 d.unwrap()

pycats/pycats/data/result.py in unwrap(self)
    163     def unwrap(self):
    164         if isinstance(self.value, Exception):
--> 165             raise self.value
    166         return self.value

pycats/pycats/data/result.py in wrapped_func(*args, **kwargs)
    110         def wrapped_func(*args, **kwargs):
    111             try:
--> 112                 return Ok(func(*args, **kwargs))
    113             except Exception as e:
    114                 return Err(e)

<ipython-input-1-e472ddea34ee> in divide(a, b)
      4 @Result.wrap
      5 def divide(a, b):
----> 6     return a / b
      7 
      8 

ZeroDivisionError: division by zero

It would be helpful if the traceback included the line which actually called the wrapped function:

d = divide(2, 0)

instead of skipping from the .unwrap() call straight to inside the wrapped function. In a long chain of operations, it could be difficult to debug which operation was causing the exception.