Fix for browsers without ES6 support (#64)

* Fix for older browsers without ES6 support

muk_web_utils/static/src/js/underscore.js

@@ -18,7 +18,9 @@
 **********************************************************************************/
 
 _.mixin({
-	memoizeDebounce: function(func, wait=0, options={}) {
+	memoizeDebounce: function(func, wait, options) {
+		wait = (typeof wait !== 'undefined') ? wait : 0;
+		options = (typeof options !== 'undefined') ? options : {};
     	var mem = _.memoize(function() {
     		return _.debounce(func, wait, options)
     	}, options.resolver);
@@ -29,7 +31,9 @@ _.mixin({
 });
 
 _.mixin({
-    memoizeThrottle: function(func, wait=0, options={}) {
+    memoizeThrottle: function(func, wait, options) {
+		wait = (typeof wait !== 'undefined') ? wait : 0;
+		options = (typeof options !== 'undefined') ? options : {};
     	var mem = _.memoize(function() {
     		return _.throttle(func, wait, options)
     	}, options.resolver);