Slices should not raise IndexError

[jayvdb]

It is a nice oddity of slices that they never raise an IndexError. I've found two uses of slices which cause them.

>>> [0, 1, 2, 3][slice(99,-99)]
[]
>>> AllStrings("[abcdef]")[slice(99,-99)]
Traceback (most recent call last):
  File "sre_yield/__init__.py", line 137, in __getitem__
    result = SlicedSequence(self, slicer=i)
  File "sre_yield/__init__.py", line 167, in __init__
    self.start, self.stop, self.step = slice_indices(slicer, raw.__len__())
  File "sre_yield/__init__.py", line 97, in slice_indices
    stop = _adjust_index(stop, size)
  File "sre_yield/__init__.py", line 107, in _adjust_index
    raise IndexError("Out of range")
IndexError: Out of range

>>> "abcdef"[99::-1]
'fedcba'
>>> AllStrings("[abcdef]")[99::-1]
Traceback (most recent call last):
  File "sre_yield/__init__.py", line 140, in __getitem__
    result = [item for item in result]
  File "sre_yield/__init__.py", line 140, in <listcomp>
    result = [item for item in result]
  File "sre_yield/__init__.py", line 148, in __iter__
    yield self.get_item(i)
  File "sre_yield/__init__.py", line 176, in get_item
    return self.raw[j]
  File "sre_yield/__init__.py", line 144, in __getitem__
    return self.get_item(i)
  File "re_yield/__init__.py", line 405, in get_item
    return super().get_item(i)
  File "sre_yield/__init__.py", line 126, in get_item
    return self.raw.get_item(i, d)
  File "sre_yield/__init__.py", line 217, in get_item
    raise IndexError("Index %d out of bounds" % (i,))
IndexError: Index 6 out of bounds