added possibility to cast any key to any type using any method

spec/couchrest/core/model_spec.rb

@@ -88,6 +88,12 @@ class Player < CouchRest::Model
   timestamps!
 end
 
+class Event < CouchRest::Model
+  key_accessor :subject, :occurs_at
+
+  cast :occurs_at, :as => 'Time', :send => 'parse'
+end
+
 describe "save bug" do
   it "should fix" do
     @db = reset_test_db!
@@ -314,6 +320,18 @@ describe CouchRest::Model do
     end
   end
 
+  describe "cast keys to any type" do
+    before(:all) do
+      event_doc = { :subject => "Some event", :occurs_at => Time.now }
+      e = Event.database.save event_doc
+
+      @event = Event.get e['id']
+    end
+    it "should cast created_at to Time" do
+      @event['occurs_at'].should be_an_instance_of(Time)
+    end
+  end
+
   describe "saving a model" do
     before(:all) do
       @obj = Basic.new
@@ -679,4 +697,4 @@ describe CouchRest::Model do
       lambda{Basic.get(@obj.id)}.should raise_error
     end
   end
-end
+end