added support for scan_index_forward when chaining, made it so start …

…when chaining works correctly.

lib/dynamoid/criteria.rb

@@ -9,7 +9,7 @@ module Criteria
 
     module ClassMethods
 
-      [:where, :all, :first, :each, :limit, :start].each do |meth|
+      [:where, :all, :first, :each, :limit, :start, :scan_index_forward].each do |meth|
         # Return a criteria chain in response to a method that will begin or end a chain. For more information, 
         # see Dynamoid::Criteria::Chain.
         #

lib/dynamoid/criteria/chain.rb

@@ -16,6 +16,7 @@ def initialize(source)
         @query = {}
         @source = source
         @consistent_read = false
+        @scan_index_forward = true
       end
 
       # The workhorse method of the criteria chain. Each key in the passed in hash will become another criteria that the
@@ -63,6 +64,11 @@ def start(start)
         self
       end
 
+      def scan_index_forward(scan_index_forward)
+        @scan_index_forward = scan_index_forward
+        self
+      end
+
       # Allows you to use the results of a search as an enumerable over the results found.
       #
       # @since 0.2.0
@@ -227,6 +233,7 @@ def query_opts
         opts = {}
         opts[:limit] = @limit if @limit
         opts[:next_token] = start_key if @start
+        opts[:scan_index_forward] = @scan_index_forward
         opts
       end
     end