Adding charAt in keypath parse to be more compatiable with older browsers that d…

…ont support the array operator when iterating throught strings.  Simple hello world test page can be found here http://softgpl.com/rivets/ie7/index.html

@@ -8,7 +8,8 @@ class Rivets.KeypathParser
     tokens = []
     current = {interface: root, path: ''}
 
-    for char in keypath
+    for index in [0...keypath.length] by 1
+      char = keypath.charAt index
       if char in interfaces
         tokens.push current
         current = {interface: char, path: ''}