Fix + test for #90
Merge pull request #91 from baruchoxman/master

Fix + test for #90
searching for {'propertyName' : None}  and {'propertyName.subProp' : None} was inconsistent with MongoDb
allow with_limit_and_skip to be passed to cursor count method
Merge pull request #92 from texuf/master

searching for {'propertyName' : None}  and {'propertyName.subProp' : Non...
Merge pull request #93 from emirose/cursor_count_method_with_arg

allow with_limit_and_skip to be passed to cursor count method
Credits
Connection.__init__(): set document_class
Merge pull request #94 from hatchddigital/master

Connection.__init__(): set document_class
Acknowledgements
add group and aggregate functions
fix parameters on group and aggregate to match pymongo
failing test for reduce
skip the new group and aggregate tests if execs and pymongo aren't installed
Merge pull request #1 from texuf/master

fix parameters on group and aggregate to match pymongo
Refactor reduce_ctx in group, simplify group, remove ungrouped key, value pairs from group results.
Remove initial parameter from reduce_ctx call in group()
remove bad merge
initialize reduced val to proper value
make the group/agregate functions inherit from _CollectionComparisonTest, write more broken tests