Add simple filter for trimming strings.

Author: addyosmani

demo.html

@@ -70,6 +70,9 @@ <h3>last</h3>
     <h3>random</h3>
     {{ colors | random }}
 
+    <h3>trim</h3>
+    {{' I was a string with leading and trailing whitespace    ' | trim}}
+
 </template>
   <script>
 	var template = document.getElementById('view');

filter-trim.js

@@ -0,0 +1,8 @@
+/**
+ * Trim a string, removing leading and trailing whitespace
+ * @param  {string} input
+ * @return {string} trimmed string
+ */
+PolymerExpressions.prototype.trim = function(input){
+	return input.replace(/^\s*|\s*$/g, '');
+}

polymer-filters.html

@@ -11,6 +11,7 @@
 <script src="filter-wordcount.js"></script>
 <script src="filter-random.js"></script>
 <script src="filter-round.js"></script>
+<script src="filter-trim.js"></script>
 
 <!--
 A collection of filters for formatting values of [Polymer expressions](www.polymer-project.org/docs/polymer/expressions.html) for display to users.
@@ -41,6 +42,12 @@
 
 > Hello Peeps
 
+####Trim
+
+    {{' I was a string with leading and trailing whitespace    ' | trim}}
+
+> I was a string with leading and trailing whitespace
+
 ####Date
 
     {{1288323623006 | date('yyyy-MM-dd HH:mm:ss Z')}}