Added backwards compatibility for 1.8.7 String.each returning itself (and 1.9.3 not supporting .each).

Moved for tag tests to their own test model from StandardTagTest.

lib/liquid/tags/for.rb

@@ -75,7 +75,8 @@ module Liquid
       collection = context[@collection_name]
       collection = collection.to_a if collection.is_a?(Range)
     
-      return render_else(context) unless collection.respond_to?(:each) 
+      # 1.8.7 compatibility
+      return render_else(context) unless collection.respond_to?(:each) or collection.is_a?(String)
                                                  
       from = if @attributes['offset'] == 'continue'
         context.registers[:for][@name].to_i
@@ -123,6 +124,10 @@ module Liquid
       segments = []      
       index = 0      
       yielded = 0
+
+      # 1.8.7 compatibility
+      return [collection] if collection.is_a?(String)
+
       collection.each do |item|         
                 
         if to && to <= index