Merge pull request #6274 from cirosantilli/leave-group-from-members-page

app/controllers/application_controller.rb

app/controllers/profiles/groups_controller.rb

app/controllers/users_groups_controller.rb

app/helpers/groups_helper.rb

app/models/ability.rb

app/views/groups/members.html.haml

app/views/help/permissions.html.haml

app/views/profiles/groups/index.html.haml

app/views/users_groups/_users_group.html.haml

features/admin/groups.feature

features/group.feature

features/group/create_group.feature

features/group/group.feature

features/profile/group.feature

features/steps/group/group.rb

features/steps/profile/group.rb

features/steps/project/project_network_graph.rb

features/steps/shared/authentication.rb

features/steps/shared/group.rb

features/steps/shared/paths.rb