Support a list filter

Author: cfjedimaster

demo.html

@@ -82,6 +82,12 @@ <h3>length</h3>
     <h3>trim</h3>
     {{' I was a string with leading and trailing whitespace    ' | trim}}
 
+    <h3>list</h3>
+    {{colors | list}}
+
+    <h3>list(" ")</h3>
+    {{colors | list(" ")}}
+
 </template>
   <script>
 	var template = document.getElementById('view');

filter-list.js

@@ -0,0 +1,8 @@
+/**
+ * Transform an array of strings into a readable list
+ * @param  {array} input 
+ * @return {string} array elements delimited by a comma
+ */
+PolymerExpressions.prototype.list = function(input, space){
+  return input.join("," + (space || ""));
+};

polymer-filters.html

@@ -15,6 +15,7 @@
 <script src="filter-titlecase.js"></script>
 <script src="filter-trim.js"></script>
 <script src="filter-length.js"></script>
+<script src="filter-list.js"></script>
 
 <!--
 A collection of filters for formatting values of [Polymer expressions](http://www.polymer-project.org/docs/polymer/expressions.html) for display to users.
@@ -141,6 +142,16 @@
 
 > 45.3
 
+####Converting arrays to a list
+
+    {{ arr | list }}
+
+> something,somethingelse,etc
+
+    {{ arr | list(" ") }}
+
+> something, somethingelse, etc
+
 @element polymer-filters
 @blurb A collection of Polymer filters for formatting values of expressions for display to users
 @homepage http://addyosmani.github.io/polymer-filters