Post install message for gem.

capybara.gemspec

@@ -41,4 +41,26 @@ Gem::Specification.new do |s|
     s.signing_key = 'gem-private_key.pem'
   end
   s.cert_chain = ['gem-public_cert.pem']
+
+  s.post_install_message = <<-MESSAGE
+IMPORTANT! Some of the defaults have changed in Capybara 2.1. If you're experiencing failures,
+please revert to the old behaviour by setting:
+
+    Capybara.configure do |config|
+      config.match = :one
+      config.exact_options = true
+      config.ignore_hidden_elements = true
+      config.visible_text_only = true
+    end
+
+If you're migrating from Capybara 1.x, try:
+
+    Capybara.configure do |config|
+      config.match = :prefer_exact
+      config.ignore_hidden_elements = false
+    end
+
+Details here: http://www.elabs.se/blog/60-introducing-capybara-2-1
+
+  MESSAGE
 end