Moved atoms to core_atoms
First version of zsets intersect_update
Intersect for sorted sets, upgraded tests
Disjoint test and implementation
Added difference_update for zsets
Raising an error for in-place difference calculation
Fixes for mixup with update and non update methods and symetric diff test and stub
Symmetrical difference implementation
Fixed more names mixup
Cmp testing
Slice tests passing through (tweaked tests and constructor - slice creates new instance of the object instead of a list)
Tests for unwanted in place diff methods are asserting the exception
Removed bisect test
Merge remote-tracking branch 'remotes/origin/feature/blist_collections' into feature/decayed-ranker