make block script ES5 compatible

There are polyfills for methods like apiFetch, so migrate the syntax to
ES5 (no generators, method shorthands, arrow functions, ...) and we are
done here without adding transpilers to the project.

scripts/block.js

@@ -4,43 +4,39 @@
  * Gutenberg Block to integrate the liveticker widget without shortcode.
  */
 ( function() {
-	var { __ } = wp.i18n;
-	var { registerBlockType } = wp.blocks;
-	var { registerStore, withSelect } = wp.data;
+	var __ = wp.i18n.__;
+	var registerBlockType = wp.blocks.registerBlockType;
+	var registerStore = wp.data.registerStore;
+	var withSelect = wp.data.withSelect;
 	var el = wp.element.createElement;
 
 	/**
 	 * Datastore actions.
 	 */
 	var actions = {
-		setTickers( tickers ) {
+		setTickers: function( tickers ) {
 			return {
 				type: 'SET_TICKERS',
-				tickers,
+				tickers: tickers,
 			};
 		},
-		getTickers( path ) {
+		getTickers: function( path ) {
 			return {
 				type: 'RECEIVE_TICKERS',
-				path,
-			};
-		},
-		loadTickers( path ) {
-			return {
-				type: 'LOAD_TICKERS',
-				path,
+				path: path,
 			};
 		},
 	};
 
 	registerStore( 'scliveticker/ticker', {
-		reducer( state = { tickers: null }, action ) {
+		reducer: function( state, action ) {
+			if ( undefined === state ) {
+				state = { tickers: null };
+			}
 			switch ( action.type ) {
 				case 'SET_TICKERS':
-					return {
-						...state,
-						tickers: action.tickers,
-					};
+					state.tickers = action.tickers;
+					return state;
 				case 'RECEIVE_TICKERS':
 					return action.tickers;
 			}
@@ -48,30 +44,24 @@
 			return state;
 		},
 
-		actions,
+		actions: actions,
 
 		selectors: {
-			receiveTickers( state ) {
-				const { tickers } = state;
-				return tickers;
-			},
-		},
-
-		controls: {
-			LOAD_TICKERS( action ) {
-				return wp.apiFetch( { path: action.path } );
+			receiveTickers: function( state ) {
+				return state.tickers;
 			},
 		},
 
 		resolvers: {
-			* receiveTickers() {
-				const tickers = yield actions.loadTickers( '/wp/v2/scliveticker_ticker' );
+			receiveTickers: function() {
+				return wp.apiFetch( { path: '/wp/v2/scliveticker_ticker' } ).then( function( tickers ) {
 					return actions.setTickers( tickers.map( function( t ) {
 						return {
 							name: t.name,
 							slug: t.slug,
 						};
 					} ) );
+				} );
 			},
 		},
 	} );
@@ -97,7 +87,7 @@
 				default: false,
 			},
 		},
-		edit: withSelect( ( select ) => {
+		edit: withSelect( function( select ) {
 			return {
 				tickers: select( 'scliveticker/ticker' ).receiveTickers(),
 			};