python dict implementation for Nim's Table

[cblake]

Reduced size and increased perf _compared to what_? Python's old, slow hash 
table impl? It's very easy to write your own table to beat Python's stdlib 
table, _especially_ in special circumstances like only integer keys. I used to 
do that with Cython when I used CPython, actually. That "code marketing" has 
left people with an impression otherwise is, well, hard to correct.