Added test for another issue I found.
Added test for another issue I found.

I appears that calling update(iterable) does not add all the elements
from iterable. I think the problem once again lies in grow function. All
the problems could have been solved simply by removing that crazy condition on
line 118 of veb/core.py file: "if log2(square_root).is_integer():". But
I understand why that condition is there, so I'll try to help the cause.

Julian/veb