Optionally ignore ruby env normalisation files, with comments

Rails.gitignore

@@ -3,9 +3,6 @@
 .sass-cache
 capybara-*.html
 .rspec
-.rvmrc
-/.bundle
-/vendor/bundle
 /log
 /tmp
 /db/*.sqlite3
@@ -16,3 +13,15 @@ capybara-*.html
 rerun.txt
 pickle-email-*.html
 config/initializers/secret_token.rb
+
+## Environment normalisation:
+/.bundle
+/vendor/bundle
+
+# these should be checked in to normalise the environment:
+# Gemfile.lock
+# .ruby-version
+# .ruby-gemset
+
+# unless supporting rvm < 1.11.0 or doing something fancy, ignore this:
+.rvmrc