[docs] method_override explained

- update rack docs link

docs/method_override.md

@@ -1,10 +1,10 @@
 # Method override
 
-Writes the original HTTP method to "X-Http-Method-Override" header and changes the request method to POST.
+Changes the request method to POST and writes the original HTTP method to the "X-Http-Method-Override" header.
 
-This can be used to work around technical issues with making non-POST requests, e.g. faulty HTTP client or server router.
+This can be used to work around technical issues with making non-POST requests, e.g. a faulty HTTP client or server router.
 
-This header is recognized in Rack apps by default, courtesy of the [Rack::MethodOverride](http://rack.rubyforge.org/doc/classes/Rack/MethodOverride.html) module.
+This header is recognized in Rack apps by default, courtesy of the [Rack::MethodOverride](https://www.rubydoc.info/github/rack/rack/Rack/MethodOverride) module.
 
 ```rb
 connection = Faraday.new 'http://example.com/api' do |conn|