Added last_month and next_month

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@734 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activesupport/lib/active_support/core_ext/time/calculations.rb

@@ -53,6 +53,16 @@ def months_since(months)
           end
         end
 
+        # Short-hand for months_ago(1)
+        def last_month
+          months_ago(1)
+        end
+
+        # Short-hand for months_since(1)
+        def next_month
+          months_since(1)
+        end
+
         # Returns a new Time representing the "start" of this week (Monday, 0:00)
         def beginning_of_week
           (self - self.wday.days).midnight + 1.day