check if Rails exists for the rails support

lib/couchrest/support/rails.rb

@@ -1,7 +1,6 @@
 # This file contains various hacks for Rails compatibility.
-# To use, just require in environment.rb, like so:
-#
-#   require 'couchrest/support/rails'
+
+if defined?(Rails)
 
   class Hash
     # Hack so that CouchRest::Document, which descends from Hash,
@@ -12,7 +11,6 @@ class Hash
     end
   end
 
-
   CouchRest::Document.class_eval do
     # Need this when passing doc to a resourceful route
     alias_method :to_param, :id
@@ -50,3 +48,5 @@ CouchRest::Validation::ValidationErrors.class_eval do
       errors.values.inject(0) { |error_count, errors_for_attribute| error_count + errors_for_attribute.size }
     end
   end
+
+end