v0.1.5 - Added groupMemberships aggregation extension functions!

Added groupMemberships aggregation extension function in ContactData.

The groupMemberships aggregation extension functions were previously commented out because it may be unsafe for consumers to use as it may cause confusion to those unfamiliar with how Groups and GroupMemberships worked.

However, having these extensions may prove to be useful when showing group memberships of multiple raw contacts to matching Groups from different accounts.

a lot of documentation in the extension function is provided to minimize risk of misuse and confusion =)