Document switch_state and refresh_i18n.
Documentation for fetch_config_value and fetch_translations.
Document setup_config, setup_metrics, user_key, load_user and store_user.
Document on_unknown_command, log, done and api_request methods.
Document reply, on_inbound_message and on_inbound_event.
Document cmd parameter to on_unknown_command.
Fix typo in on_inbound_message docstring.
Merge branch 'feature/issue-39-finish-documenting-interaction-machine' into develop