DW: Owner cannot remove self from project if there is no other owner
DW: Corrected flake8 issues
DW: Checks if user is less or equal to one
ME/DW: Added remove user serializer
DW: Code refactor
DW: Code refactor
DW: Updated the doc string
Merge pull request #739 from onaio/735_owner_cant_leave_project

735 owner cant leave project