[DOCS] Changed "Why Aluminum?" to a level one header

This commit changes "Why Aluminum?" to a level one header on the homepage of the documentation.

docs/index.rst

@@ -13,7 +13,7 @@ What is Aluminum?
 Aluminum is a lightweight web server written entirely in `Node.js <https://www.nodejs.org>`_, "an asynchronous event-driven JavaScript runtime ... designed to build scalable network applications." It includes not only a traditional static file server, but also various other features that simplify the web development process, such as an authentication server and a network-based cryptography server.
 
 Why Aluminum?
--------------
+=============
 
 Aluminum is simple to install and easy to use. Simply clone the git repository, install the dependencies automatically with ``yarn``, and copy the default configuration files into the higher level directory. Starting the web server is as simple as typing ``yarn run start`` into your terminal.