support permanent redirect, add document in readme

Author: allenwei

README.markdown

@@ -213,6 +213,19 @@ cookies[:counter] = {
 }
 cookies[:counter][:value] +=1
 ```
+## Redirect
+
+You can redirect to a new url
+
+``` ruby
+redirect "/new_url"
+```
+
+use permanent redirect
+
+``` ruby
+redirect "/new_url", true
+```
 
 ## Raising Errors
 

lib/grape/endpoint.rb

@@ -136,11 +136,16 @@ def error!(message, status=403)
     # Redirect to a new url.
     # 
     # @param url [String] The url to be redirect.
-    def redirect(url)
-      if env['HTTP_VERSION'] == 'HTTP/1.1' && request.request_method.to_s.upcase != "GET"
-        status 303
-      else 
-        status 302
+    # @param permanent [Boolean] Whether use permanent redirect with status code 304.
+    def redirect(url, permanent=false)
+      if permanent
+        status 304
+      else
+        if env['HTTP_VERSION'] == 'HTTP/1.1' && request.request_method.to_s.upcase != "GET"
+          status 303
+        else 
+          status 302
+        end
       end
       header "Location", url
       body ""

spec/grape/endpoint_spec.rb

@@ -224,6 +224,16 @@ def app; subject end
       last_response.status.should eq 303
       last_response.headers['Location'].should eq "/ha"
     end
+
+    it "support permanent redirect" do 
+      subject.get('/hey') do 
+        redirect "/ha", true
+      end
+      get '/hey'
+      last_response.status.should eq 304
+      last_response.headers['Location'].should eq "/ha"
+      last_response.body.should eq ""
+    end
   end
 
   it 'should not persist params between calls' do