Handle exclusive intervals in _get_zelement_range and related functions
Added tests for exclusive sets intervals
Added missing testing case
Cover more tests
Refactor zrange filter code to use comparator functions

This removes the code duplication in having to check for
inclusive/exclusive ranges for the various sorted set functions.
Merge branch 'allanino-exclusive-sets-interval'

* allanino-exclusive-sets-interval:
  Refactor zrange filter code to use comparator functions
  Cover more tests
  Added missing testing case
  Added tests for exclusive sets intervals
  Handle exclusive intervals in _get_zelement_range and related functions