KeysView doesn't raise RuntimeError when dict length changed.

[osoken]

Expected behavior:

>>> import sqlitecollections as sc
>>> x =  sc.Dict({"A": 1, "B": 2, "C": 3})
>>> for k in x.keys():
...     print(k)
...     x["d"] = 12
... 
A
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
RuntimeError: dictionary changed size during iteration

Actual behavior on v0.9.5

>>> for k in x.keys():
...     print(k)
...     x["d"] = 12
... 
A
B
C
d
>>>