.remove() complains on nonexistant keys; .discard() doesn't care
.pop() fails on empty set
.clear(), .update() and |= on sets
optimize in-redis operation
set intersection operations
set substraction operations
set xor operations
factor out each object type
a dict iterates on its keys
falsy values can be stored too
naive pop()
make .pop() atomic
factorize common redis object things
hash .update() method
bitmap as a set of integers
Merge pull request #6 from javierguerragiraldez/master

more set functionality