Fix SVHN path handling.

if path ended with "/", it was not correctly working.
Fix GPU pooling code. This probably don't caused problem as normally the region is square.
reuse the same argument name in the doc as elsewhere.
Add the flops method to some ops.
fix doc.
Fix crash in the creation of pytables datasets
Update doc about Alex's K. implementation.
fix join of file name path.
Fix the handling of pytable filters.
Merge pull request #449 from nouiz/flops

[MRG]Flops and fixes.