Add tests for auto configure slash commands

app/controllers/projects/services_controller.rb

app/helpers/mattermost_helper.rb

app/views/projects/services/_form.html.haml

...ojects/services/mattermost_slash_commands/_form.html.haml

app/views/shared/_service_settings.html.haml

config/routes/project.rb

lib/mattermost/command.rb

lib/mattermost/team.rb

spec/fixtures/mattermost_initial_load.json

spec/fixtures/mattermost_new_command.json

spec/lib/mattermost/command_spec.rb

spec/lib/mattermost/team_spec.rb

...roject_services/mattermost_slash_commands_service_spec.rb