📝 Normalise titles and update "sink server" link

README.md

@@ -2,13 +2,13 @@
 [![Build Status](https://travis-ci.com/gam6itko/sparkpost-mailer.svg?branch=master)](https://travis-ci.com/gam6itko/sparkpost-mailer)
 [![Coverage Status](https://coveralls.io/repos/github/gam6itko/sparkpost-mailer/badge.svg?branch=master)](https://coveralls.io/github/gam6itko/sparkpost-mailer?branch=master)
 
-## install
+## Installation
 
 ```bash
 composer require gam6itko/sparkpost-mailer
 ```
 
-## configuration
+## Configuration
 
 ### services.yaml
 ```yaml
@@ -40,10 +40,10 @@ MAILER_DSN=sparkpost+api://api_key@default?region=eu
 MAILER_DSN=sparkpost+smtp://user:password@default:port?region=eu
 ```
 
-## tests
+## Tests
 
 ### Using sink server 
-[About sink server](https://www.sparkpost.com/docs/faq/using-sink-server/)
+[About sink server](https://support.sparkpost.com/docs/faq/using-sink-server)
 
 ```yaml
 services:
@@ -53,4 +53,4 @@ services:
 
 ## Also
 
-[Api transmissions](https://developers.sparkpost.com/api/transmissions/)
+[Sparkpost's "transmissions" API reference](https://developers.sparkpost.com/api/transmissions/)